U.S. patent application number 15/776220 was filed with the patent office on 2020-08-06 for nanofiltration composite membranes comprising self-assembled supramolecular separation layer.
This patent application is currently assigned to BASF SE. The applicant listed for this patent is BASF SE. Invention is credited to Karsten SEIDEL, Kai WERLE, Natalia WIDJOJO, Wendel WOHLLEBEN.
Application Number | 20200246761 15/776220 |
Document ID | / |
Family ID | 1000004839085 |
Filed Date | 2020-08-06 |
![](/patent/app/20200246761/US20200246761A1-20200806-C00001.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00002.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00003.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00004.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00005.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00006.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00007.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00008.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00009.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00010.png)
![](/patent/app/20200246761/US20200246761A1-20200806-C00011.png)
View All Diagrams
United States Patent
Application |
20200246761 |
Kind Code |
A1 |
WOHLLEBEN; Wendel ; et
al. |
August 6, 2020 |
NANOFILTRATION COMPOSITE MEMBRANES COMPRISING SELF-ASSEMBLED
SUPRAMOLECULAR SEPARATION LAYER
Abstract
The present invention is directed to nanofiltration (NF)
composite membranes comprising at least one polymeric porous
substrate layer (S) and at least one porous selfassembled
supramolecular membrane layer (F); a method of preparing such
composite membranes; method of separation/filtration/purification
of heavy metal cations, inorganic anions, and organic small
molecules by applying such composite membranes; as well as filter
cartridges and filtration devices comprising said composite
membranes.
Inventors: |
WOHLLEBEN; Wendel;
(Mannheim, DE) ; SEIDEL; Karsten; (Mannheim,
DE) ; WERLE; Kai; (Mannheim, DE) ; WIDJOJO;
Natalia; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafe am Rhein |
|
DE |
|
|
Assignee: |
BASF SE
Ludwigshafe am Rhein
DE
|
Family ID: |
1000004839085 |
Appl. No.: |
15/776220 |
Filed: |
November 15, 2016 |
PCT Filed: |
November 15, 2016 |
PCT NO: |
PCT/EP2016/077714 |
371 Date: |
May 15, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 1/442 20130101;
B01D 69/12 20130101; C02F 2101/22 20130101; B01D 61/027 20130101;
B01D 69/02 20130101; C02F 2101/308 20130101; B01D 71/82 20130101;
C02F 2101/101 20130101; B01D 67/0088 20130101; B01D 71/68 20130101;
B01D 2323/36 20130101; B01D 2325/20 20130101; C02F 2101/105
20130101 |
International
Class: |
B01D 71/82 20060101
B01D071/82; B01D 61/02 20060101 B01D061/02; B01D 67/00 20060101
B01D067/00; B01D 69/12 20060101 B01D069/12; B01D 69/02 20060101
B01D069/02; B01D 71/68 20060101 B01D071/68; C02F 1/44 20060101
C02F001/44 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2015 |
EP |
15194732.2 |
Claims
1. A nanofiltration composite membrane, comprising: a polymeric
porous substrate layer (S) comprising a substrate layer forming
polymer (P1), wherein the polymeric porous substrate layer (S) has
a mean pore size of from 10 to 150 nm, and a porous self-assembled
supramolecular membrane layer (F) comprising, supramolecular
fibrils of a self-assembled perylene diimide deposited on the
polymeric porous substrate layer (S), wherein the porous
self-assembled supramolecular membrane layer (F) is obtained by
passing through the polymeric porous substrate layer (S) a solution
comprising supramolecular fibrils of the self-assembled perylene
diimide in an aqueous solvent, which comprises THF as an organic
cosolvent in a proportion of 1 Vol.-% or more, based on a total
volume of the solution.
2. The nanofiltration composite membrane of claim 1, wherein the
aqueous solvent comprises the THF in a proportion of up to 30
Vol.-%, based on the total volume of the solution.
3. The nanofiltration composite membrane of claim 1, wherein the
aqueous solvent comprises the THF in a proportion of from 1 to 30
Vol.-%, based on the total volume of the solution.
4. The nanofiltration composite membrane of claim 1, wherein the
nanofiltration composite membrane is further characterized by at
least one of following ion retention parameters: i) Pb.sup.2+
retention of at least 5%; and ii) PO.sub.4.sup.3- retention of at
least 10%.
5. The nanofiltration composite membrane of by claim 1, wherein the
nanofiltration composite membrane has a flux of from 10 to 80
L/m.sup.2/bar/h, as determined under standardized conditions.
6. The nanofiltration composite membrane of claim 1, wherein the
porous self-assembled supramolecular membrane layer (F) has a mean
pore size of from 1 to 10 nm.
7. The nanofiltration composite membrane of claim 1, wherein the
polymeric porous substrate layer (S) has a mean pore size of from
10 to 100 nm.
8. The nanofiltration composite membrane of claim 1, wherein the
self-assembled perylene diimide, comprises a perylene diimide of
Formula I or a salt or metal complex thereof: ##STR00010## wherein
R.sub.1 and R.sub.1' are each independently
[(CH.sub.2).sub.qO].sub.rCH.sub.3, [(CH.sub.2).sub.qO].sub.rH
[(CH.sub.2).sub.qC(O)O].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)NH].sub.rCH.sub.36,
[(CH.sub.2).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.ident.CH].sub.rCH.sub.3,
[(CH.sub.2).sub.qNH].sub.rCH.sub.3,
[(alkylene).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(alkylene).sub.qCH.ident.CH].sub.rCH.sub.3,
[(alkylene).sub.qNH].sub.rCH.sub.3, (C.sub.1-C.sub.32)alkyl,
(C.sub.3-C.sub.8)cycloalkyl, aryl, heteroaryl, chiral group,
(C.sub.1-C.sub.32)alkyl-COOH, (C.sub.1-C.sub.32)alkyl-Si--A, or
[C(O)CHR.sub.3NH].sub.pH wherein the aryl or heteroaryl groups are
optionally substituted by 1-3 groups comprising halide, CN,
CO.sub.2H, OH, SH, NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl) or
O--(C.sub.1-C.sub.6 alkyl); wherein A comprises three same or
different substituents of Cl, Br, I, O(C.sub.1-C.sub.8)alkyl or
(C.sub.1-C.sub.8)alkyl; and wherein R.sub.3 in the
[C(O)CHR.sub.3NH].sub.pH is an alkyl, haloalkyl, hydroxyalkyl,
hydroxyl, aryl, phenyl, phenylalkyl, aminoalkyl and independently
the same or different when p is larger than 1; R.sub.2 and R.sub.2'
are each independently [(CH.sub.2).sub.qO].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)O].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)NH].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.ident.CH].sub.rCH.sub.3,
[(CH.sub.2).sub.qNH].sub.rCH.sub.3,
[(alkylene).sub.qO].sub.rCH.sub.3,
[(alkylene).sub.qC(O)O].sub.rCH.sub.3,
[(alkylene).sub.qC(O)NH].sub.rCH.sub.3,
[(alkylene).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(alkylene).sub.qCH.ident.CH].sub.rCH.sub.3,
[(alkylene).sub.qNH].sub.rCH.sub.3, (C.sub.1-C.sub.32)alkyl,
(C.sub.3-C.sub.8)cycloalkyl, aryl, heteroaryl, chiral group,
(C.sub.1-C.sub.32)alkyl-COOH, (C.sub.1-C.sub.32)alkyl-Si--A, or
[C(O)CHR.sub.4NH].sub.sH wherein the aryl or heteroaryl groups are
optionally substituted by 1-3 groups comprising halide, CN,
CO.sub.2H, OH, SH, NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl) or
O-(C.sub.1-C.sub.6 alkyl); wherein A comprises three same or
different substituents of Cl, Br, I, O-(C.sub.1-C.sub.8)alkyl or
(C.sub.1-C.sub.8)alkyl; and wherein R.sub.4 in the
[C(O)CHR.sub.4NH].sub.sH is an alkyl, haloalkyl, hydroxyalkyl,
hydroxyl, aryl, phenyl, phenylalkyl, aminoalkyl and independently
the same or different when s is larger than 1; R.sub.5 and R.sub.5'
are each independently H, --OR.sub.x where R.sub.x is
C.sub.1-C.sub.6 alkyl, [(CH.sub.2).sub.nO].sub.oCH.sub.3 or
[(CH.sub.2).sub.nO].sub.oH; [(CH.sub.2).sub.nC(O)O].sub.oCH.sub.3,
[(CH.sub.2).sub.nC(O)NH].sub.oCH.sub.3,
[(CH.sub.2).sub.nCH.sub.2.dbd.CH.sub.2].sub.oCH.sub.3,
[(CH.sub.2).sub.nCH.ident.CH].sub.oCH.sub.3,
[(CH.sub.2).sub.nNH].sub.oCH.sub.3,
[(alkylene).sub.nO].sub.oCH.sub.3,
[(alkylene).sub.nC(O)O].sub.oCH.sub.3,
[(alkylene).sub.nC(O)NH].sub.oCH.sub.3,
[(alkylene).sub.nCH.sub.2.dbd.CH.sub.2].sub.oCH.sub.3,
[(alkylene).sub.nCH.ident.CH].sub.oCH.sub.3,
[(alkylene).sub.nNH].sub.oCH.sub.3, aryl, heteroaryl,
CH.ident.C-R.sub.7, CH.dbd.R.sub.8R.sub.9, NR.sub.10R.sub.11,
chiral group, amino acid, peptide or a saturated carbocyclic or
heterocyclic ring wherein the saturated heterocyclic ring or
heteroaryl contains comprises at least one nitrogen atom and
R.sub.5 or R.sub.5' are connected via the at least one nitrogen
atom and wherein the saturated carbocyclic ring, heterocyclic ring,
aryl and heteroaryl groups are optionally substituted by 1-3 groups
comprising halide, aryl, heteroaryl, CN, CO.sub.2H, OH, SH,
NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl) or O-(C.sub.1-C.sub.6
alkyl); R.sub.7 is H, halo, (C.sub.1-C.sub.32)alkyl, aryl,
NH.sub.2, alkyl-amino, COOH, C(O)H, alkyl-COOH heteroaryl,
Si(H).sub.3 or Si[(C.sub.1-C.sub.8)alkyl].sub.3 wherein the aryl or
heteroaryl groups are optionally substituted by 1-3 groups
comprising halide, aryl, heteroaryl, CN, CO.sub.2H, OH, SH,
NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl) or O-(C.sub.1-C.sub.6
alkyl); R.sub.8, R.sub.9, R.sub.10 and R.sub.11 are each
independently H, (C.sub.1-C.sub.32)alkyl, aryl, NH.sub.2,
alkyl-amino, COOH, C(O)H, alkyl-COOH or heteroaryl wherein [[said]]
the aryl or heteroaryl groups are optionally substituted by 1-3
groups comprising halide, CN, CO.sub.2H, OH, SH, NH.sub.2,
CO.sub.2-(C.sub.1-C.sub.6 alkyl) or O-(C.sub.1-C.sub.6 alkyl); L is
a linker; n is an integer from 1 to 5; o is an integer from 1 to
100; p is an integer from 1 to 100; q is an integer from 1 to 5; r
is an integer from 1 to 100; and s is an integer from 1 to 100;
wherein if R.sub.5 and/or R.sub.5' are chiral; the nanofiltration
composite membrane forms a chiral membrane.
9. The nanofiltration composite membrane of claim 6, wherein L is
selected from linkers of formulae (a) to (f) ##STR00011## R.sub.1
and R.sub.1' are each independently (C.sub.1-C.sub.32)alkyl,
R.sub.2 and R.sub.2' are each independently (C.sub.1-C.sub.32)alkyl
or (C.sub.3-C.sub.10)alkyl, R.sub.5 and R.sub.5' are each
independently [(CH.sub.2).sub.nO].sub.oCH.sub.3 or
[(CH.sub.2).sub.nO].sub.oH; n is an integer from 1 to 5; and o is
an integer from 5 to 50.
10. The nanofiltration composite membrane of claim 1, wherein the
perylene diimide is a compound of Formula II: ##STR00012## wherein
PEG is a polyethylene glycol residue comprising from 10 to 25
consecutive ethylene glycol units (PEG10 to PEG25), or a mixture of
at least two of the compounds.
11. The nanofiltration composite membrane of claim 1, wherein the
polymeric porous substrate layer (S) is a polyarylene ether-based
layer.
12. The nanofiltration composite membrane of claim 1, wherein the
porous self-assembled supramolecular membrane layer (F) deposited
on top of the polymeric porous substrate layer (S) has a layer
thickness of at least 0.1 g/m.sup.2 (mass of (F) per area of
(S)).
13. The nanofiltration composite membrane of claim 1, in the form
of a flat sheet, wherein the polymeric porous substrate layer (S)
has a layer thickness of from 50 to 250 .mu.m.
14. The nanofiltration composite membrane of claim 1, in a tubular
form, wherein the polymeric porous substrate layer (S) has a layer
thickness of from 50 to 2000 .mu.m, and/or wherein the porous
self-assembled supramolecular membrane layer (F) is deposited on an
inner surface of the polymeric porous substrate layer (S).
15. A method of preparing the nanofiltration composite membrane of
claim 1, the method comprising: a) providing at least one polymeric
porous substrate layer (S), b) providing a solution comprising
supramolecular fibrils of at least one self-assembled perylene
diimide in an aqueous solvent comprising an organic co-solvent in a
proportion suitable for reducing a molecular weight of
supramolecular perylene diimide structures; wherein in b) a
solution comprising supramolecular fibrils of at least one
self-assembled perylene diimide in an aqueous solvent is applied,
wherein the aqueous solvent comprises THF as the organic co-solvent
in a proportion of 1 Vol.-% or more, based on the total volume of
the solution. c) passing the solution of b) through the polymeric
porous substrate layer of a), thereby depositing the supramolecular
fibrils of at least one self-assembled perylene diimide from the
solution onto the polymeric porous substrate layer (S) to form at
least one porous self-assembled supramolecular membrane (F),
optionally followed by washing at least one deposited porous
self-assembled supramolecular membrane with an aqueous liquid; and
e) optionally repeating b) and c) with the same solution or a
solution with different proportion of the organic co-solvent.
16. The method of claim 15, wherein the aqueous solvent comprises
the THF in a proportion of from 1 to 30 Vol.-%, based on the total
volume of the solution.
17. The method of claim 15, further comprising: d) performing a
post-deposition treatment by applying the at least one deposited
porous self-assembled supramolecular membrane (F) with an
aqueous-alkanolic solvent.
18. A method of separation, filtration and/or purification of at
least one metal cation and/or at least one inorganic anions anion,
the method comprising: passing an aqueous medium comprising a metal
cation and/or an inorganic anion through the nanofiltration
composite membrane of claim 1, thereby obtaining an aqueous
filtrate depleted from at least one of the metal cation and the
inorganic anion and a retentate enriched with at least one of the
metal cation and the inorganic anion.
19. A method of separation or filtration of at least one water
soluble organic molecule, the method comprising: passing an aqueous
medium comprising a water soluble organic molecule through the
nanofiltration composite membrane of claim 1, thereby obtaining an
aqueous filtrate depleted from at least one dye and a retentate
enriched with the at least one dye.
20. A filter cartridge, comprising: the nanofiltration composite
membrane of of claim 1, in a tubular form, wherein the porous
self-assembled supramolecular membrane layer (F) is deposited on an
inner surface of the polymeric porous substrate layer (S).
21. A filtration device, comprising the filter cartridge of claim
20.
22. The method of claim 15, wherein the nanofiltration composite
membrane as applied therein has a permeance of from 1 to 200
L/m.sup.2/h/bar.
23. The nanofilteration composite membrane of claim 1, in the form
of a flat sheet.
24. The nanofiltration composite membrane of claim 1, in the form
of a multibore hollow fibre.
25. A filter cartridge, comprising the nanofiltration composite
membrane of claim 1, in the form of a flat sheet.
Description
[0001] The present invention is directed to nanofiltration (NF)
composite membranes comprising at least one polymeric porous
substrate layer (S) and at least one porous self-assembled
supramolecular membrane layer (F); a method of preparing such
composite membranes; method of separation/filtration/purification
of heavy metal cations, inorganic anions, and organic small
molecules by applying such composite membranes; as well as filter
cartridges and filtration devices comprising said composite
membranes.
BACKGROUND OF THE INVENTION
[0002] Nanofiltration (NF) is a pressure-driven technique that is
gaining popularity due to its low consumption of energy, high water
permeability and retention of multivalent ions as compared to the
well-established reverse osmosis process [B. Van Der Bruggen, C.
Vandecasteele, T. Van Gestel, W. Doyen, R. Leysen, A review of
pressure-driven membrane processes in wastewater treatment and
drinking water production, Environmental Progress, 22 (2003) 46-56;
X.-L. Li, L.-P. Zhu, Y.-Y. Xu, Z. Yi, B.-K. Zhu, A novel positively
charged nanofiltration membrane prepared from
N,N-dimethylaminoethyl methacrylate by quaternization
cross-linking, Journal of Membrane Science, 374 (2011) 33-42.].
Such membranes have been researched for the application in many
areas such as pre-treatment for the desalination process and have
shown to be able to remove turbidity, microorganisms and dissolved
salts .
[0003] A NF membrane usually consists of a thin active layer (or
separating layer) supported by a porous sublayer or substrate
layer. This active layer plays the determining role in permeation
and separation characteristics while the porous sublayer imparts
the mechanical strength. There are many approaches to fabricate
this active layer, namely:
[0004] (1) interfacial polymerization [T. K. Dey, R. C. Bindal, S.
Prabhakar, P. K. Tewari, Development, Characterization and
Performance Evaluation of Positively-Charged Thin Film-Composite
Nanofiltration Membrane Containing Fixed Quaternary Ammonium
Moieties, Separation Science and Technology, 46 (2011) 933-943.],
(2) layer-by-layer assembly [L. Ouyang, R. Malaisamy, M. L.
Bruening, Multilayer polyelectrolyte films as nanofiltration
membranes for separating monovalent and divalent cations, Journal
of Membrane Science, 310 (2008) 76-84; B. W. Stanton, J. J. Harris,
M. D. Miller, M. L. Bruening, Ultrathin, Multilayered
Polyelectrolyte Films as Nanofiltration Membranes, Langmuir, 19
(2003) 7038-7042.], (3) chemical crosslinking [R. Huang, G. Chen,
B. Yang, C. Gao, Positively charged composite nanofiltration
membrane from quaternized chitosan by toluene diisocyanate
cross-linking, Separation and Purification Technology, 61 (2008)
424-429.] and (4) UV grafting [S. Bequet, J.-C. Remigy, J.-C.
Rouch, J.-M. Espenan, M. Clifton, P. Aptel, From ultrafiltration to
nanofiltration hollow fiber membranes: a continuous
UV-photografting process, Desalination, 144 (2002) 9-14.].
[0005] Among these approaches, UV grafting has been applied for
years due to its advantages such as ease of operation and low cost
[M. Ulbricht, H.-H. Schwarz, Novel high performance photo-graft
composite membranes for separation of organic liquids by
pervaporation, Journal of Membrane Science, 136 (1997) 25-33; J.
Pieracci, D. W. Wood, J. V. Crivello, G. Belfort, UV-Assisted Graft
Polymerization of N-vinyl-2-pyrrolidinone onto Poly(ether sulfone)
Ultrafiltration Membranes: Comparison of Dip versus Immersion
Modification Techniques, Chemistry of Materials, 12 (2000)
2123-2133.]. In addition, the fabrication via UV grafting produces
an integral selective layer due to a strong chemical bond to the
substrate which provides sufficient mechanical stability under
relatively high operating pressure.
[0006] It has been known that polyethersulfone (PESU) can generate
free radicals upon exposure to UV light due its photosensitive
nature [H. Yamagishi, J. V. Crivello, G. Belfort, Development of a
novel photochemical technique for modifying poly (arylsulfone)
ultrafiltration membranes, Journal of Membrane Science, 105 (1995)
237-247.]. Thus, vinyl monomers in contact with free radicals can
form a covalent bond with PESU.
[0007] The separation behaviour of NF membranes comprises size
exclusion as well as electrostatic repulsion [M. Mulder, Basic
Principles of Membrane Technology, 2nd Ed., Kluwer Academic
Publishers, Netherlands, 19964].
[0008] WO 2015/000801 describes multiple channel membranes
comprising multiple longitudinal channels formed within a polymer
based carrier and further comprising a polymeric separation layer
formed on the inner surface of each of said longitudinal
channels.
[0009] WO2012/025928 describes recyclable membranes suitable for
the separation of nanomaterials. Said membranes are made of
self-assembled perylene imide derivatives. Said prior art documents
exemplifies the applicability of said membranes for the separation
of gold particles and protein molecules such as bovine serum
albumin (molecular weight 67 kDa). For this purpose the perylene
material is deposited on conventional cellulose acetate support
membranes having a pore size around 450 nm. The applicability of
such perylene imide materials for the separation of very small
molecules or even ions, like metal cations or inorganic small
anions, has not been investigated so far.
[0010] There is a need of further improved membrane materials which
are mechanically stable, easy to manufacture and applicable in the
separation of small inorganic ions, metal cations, and small
inorganic ions, like nitrate, and which optionally further improved
by a reduced tendency of membrane fouling.
SUMMARY OF THE INVENTION
[0011] The above problem is, in particular, solved by providing a
new type of composite membrane material as defined in the
claims.
BRIEF DESCRIPTION OF DRAWING
[0012] FIG. 1 shows the UV-Vis spectrum of the liquid medium before
(black, dotted line) and after passing a NADIR UP150 type PES
supporting membrane (black line). Said medium contained in an
aqueous phase containing 3% (v/v) THF the supramolecular membrane
layer forming compound PP2b (1 mg/ml).The spectra clearly show that
PP2b was quantitatively deposited.
[0013] FIG. 2 illustrates the influence of an increasing THF
concentration on the fibrille size before PP2b deposition. 1% THF
(dash-dotted line); 3% THF (dotted line); 6% THF (dashed line); 10%
THF(solid line).
[0014] FIG. 3 illustrates the successful deposition of PP2b inside
INGE Multibore.RTM. (surface area 41 cm.sup.2). The UV-Vis spectrum
of the liquid medium before (light grey) and after passing PP2b in
a 3% THF solvent (grey) and 6% THF solvent (black) through a NADIR
type PES supporting membrane.
[0015] FIG. 4 illustrates the reduction of membrane fouling by
PP2b. As fouling simulants milk powder (black) and humic acids
(grey) were examined.
DETAILED DESCRIPTION OF THE INVENTION
[0016] A. General Definitions.
[0017] In the context of the present invention a "membrane"
generally shall be understood to be a thin, semipermeable porous
structure capable of separating two fluids or in particular,
separating uncharged molecules and/or ionic components or small
particles from a liquid. The membrane acts as a size selective
barrier, allowing certain particles, substances or chemicals to
pass through while retaining others. If not otherwise stated, a
membrane comprises organic polymers as the main components. Such
polymer shall be considered the main component of a membrane if it
is comprised in an amount of at least 50% by weight, preferably at
least 60%, more preferably at least 70%, even more preferably at
least 80% and particularly preferably at least 90% by weight of the
final membrane.
[0018] "Membranes for water treatment" are generally semi-permeable
membranes which allow for separation of dissolved and suspended
particles of water, wherein the separation process itself can be
either pressure-driven or electrically driven.
[0019] "Pressure-driven" membrane technologies comprise
microfiltration (MF; typical pore size about 0.08 to 2 .mu.m, for
separation of very small, suspended particles, colloids, bacteria),
ultrafiltration (UF; typical pore size about 0.005 to 0.2 .mu.m;
for separation of organic particles>1000 MW, viruses, bacteria,
colloids), nanofiltration (NF, typical pore size 0.001 to 0.01
.mu.m, for separation of organic particles>300 MW Trihalomethan
(THM) precursors, viruses, bacteria, colloids, dissolved solids) or
reverse osmosis (RO, typical pore size 0.0001 to 0.001 .mu.m, for
separation of ions, organic substances>100 MW).
[0020] "Molecular weights" of polymers are, unless otherwise stated
as Mw values, in particular determined via GPC in DMAc. In
particular, the GPC measurements were performed with
dimethylacetamide (DMAc) containing 0.5 wt-% lithium bromide.
Polyester copolymers were used as column material. The calibration
of the columns was performed with narrowly distributed PMMA
standards. As flow rate 1 ml/min was selected, the concentration of
the injected polymer solution was 4 mg/ml.
[0021] A "substrate layer" of the present invention also shows a
porous structure, is permeable for those constituents that also
pass through the "separation layer" and may also be designated as
"membrane". It may also be designated as "carrier" or "carrier
membrane" or as a "support", "support layer", "support membrane",
or "scaffold layer". If not otherwise stated such carriers normally
have an average pore diameter of 0.5 nm to 1000 nm, preferably 1 to
40 nm, more preferably 10 to 50 nm.
[0022] A "separation layer" also designated as "rejection layer",
is attached to and formed on (the outer surface of) the carrier or
substrate layer. The separation layer normally is in direct contact
with the liquid medium.
[0023] A "composite membrane" comprises at least one substrate
layer as defined above associated with at least one separation
layer as defined above. "Associated with" encompasses any type of
interaction between substrate and separation layer, which allows a
reversible (in particular by ionic of hydrophobic interactions) or
irreversible (in particular by forming covalent chemical bonds)
ligation of said two layers. Preferred in the context of the
present invention are reversible, non-covalent interactions between
substrate and separation layers.
[0024] "Flat sheet membranes" show a planar structure and comprise
at least one substrate layer and on to a least one separation layer
as defined above.
[0025] A "hollow fiber membrane" is composed of a substrate in the
form of a hollow fiber which in turn carries at its inner or outer
surface least one separation layer as defined above. The liquid
medium to be treated normally passes through the inside of the
fiber
[0026] "Multiple channel membranes", also referred to as multibore
membranes, comprise more than one longitudinal channels also
referred to simply as "channels". It may also be considered as
bundle of hollow fiber membranes embedded in a carrier or substrate
matrix, which forms a porous substrate around said individual
channels, through which the liquid medium to be treated passes
through.
[0027] An "asymmetric membrane" (or anisotropic membrane) has a
thin porous or nonporous selective barrier, supported by a much
thicker porous substructure (see also H. Susanto, M. Ulbricht,
Membrane Operations, Innovative Separations and Transformations,
ed. E. Driolo, L. Giorno, Wiley-VCH-Verlag GmbH, Weinheim, 2009, p.
21).
[0028] If not otherwise stated herein, a "polyethersulfone"
(abbreviated as PES or PESU) in the context of the invention has to
be under stood broadly, in not otherwise stated, and is intended to
denote any polyethersulfone polymers, each of which is composed of
more than about 30, more than about 40, in particular more than
about 50 wt. %, preferably more than about 80 wt.-%, and most
preferably more than about 90 wt.-% of recurring units that contain
at least one ether group (--O--) and at least one sulfone group
(--SO.sub.2--). Preferred PES polymers are poly(arylethersulfone)
polymers, which, additionally comprise at least one, like 1, 2, 3,
4, 5 or 6, arylene groups in its recurring unit. In addition to
said at least one ether group (--O--) and at least one sulfone
group (--SO.sub.2--), the recurring unit may also contain at least
one thioether (--S--) and/or at least one keto (--C(.dbd.O)--)
group. Preferred PES polymers are poly(arylethersulfone) polymers,
which, contain in their recurring unit arylene groups exclusively
linked via ether (--O--) and sulfone (--SO.sub.2--) groups.
[0029] A "polyarylene ether" (PAE) as used herein comprises, and
preferably is formed from, blocks of the general formula
##STR00001##
wherein [0030] t and q each independently are 0, 1, 2 or 3, [0031]
Ar and Ar.sup.1 each independently an arylene group as defined
herein below, preferably having from 6 to 18 carbon atoms.
[0032] Q, T and Y each independently a chemical bond or a group
selected from --O--, --S--, --SO.sub.2--, S.dbd.O, C.dbd.O,
--N.dbd.N--, --CR.sub.aR.sub.b-- wherein R.sub.a and R.sub.b are
each independently a hydrogen atom or a C.sub.1-C.sub.12-alkyl,
C.sub.1-C.sub.12-alkoxy or C.sub.6-C.sub.18-aryl group, or wherein
--CR.sub.aR.sub.b-- also may form a optionally substituted
1,1-cycloalkylidene group; and wherein at least one of Q, T and Y
is not --O--. Preferably at least one of Q, T and Y is
--SO.sub.2--, and in that case compounds of Formula III represent a
particular group of PES or PESU polymers.
[0033] For formula III preferred C.sub.1-C.sub.12-alkyl groups
comprise linear and branched, saturated alkyl groups having from 1
to 12 carbon atoms. Particularly preferred C.sub.1-C.sub.12-alkyl
groups are C.sub.1-C.sub.6-alkyl radicals such as methyl, ethyl,
n-propyl, isopropyl, n-butyl, secbutyl, 2- or 3-methylpentyl and
longer-chain radicals such as unbranched heptyl, octyl, nonyl,
decyl, undecyl, lauryl, and the singularly or multiply branched
analogs thereof.
[0034] For formula III preferred C.sub.1-C.sub.12-alkoxy groups
include the oxy terminated analogs of the above alkyl groups having
from 1 to 12 carbon atoms defined above.
[0035] For formula III preferred 1,1-cycloalkylidene groups
comprise especially C.sub.3-C.sub.12-cycloalkylidene radicals, for
example cyclopropyliden, cyclobutylidene, cyclopentylidene,
cyclohexyliden, cycloheptyliden, cyclooctyliden, and the
substituted analogues thereof, carrying 1 or more, like 1, 2, 3, 4,
5 or 6 lower alkyl substituents, in particular methyl or ethyl,
preferably methyl substituents.
[0036] For formula III preferred C.sub.6-C.sub.18-arylene groups Ar
and Ar.sup.1 are especially phenylene groups, such as 1,2-, 1,3-and
1,4-phenylene groups, naphthylene groups, for example 1,6-, 1,7-,
2,6- and 2,7-naphthylene, and the arylene groups derived from
anthracene, phenanthrene and naphthacene. Preferably, Ar and
Ar.sup.1 in the preferred embodiments of formula III are each
independently selected from the group consisting of 1,4-phenylene,
1,3-phenylene, naphthylene, especially 2,7-dihydroxynaphthalene,
and 4,4'-bisphenylene.
[0037] In more general terms "arylene" represents bivalent, mono-
or polynucleated, in particular mono-, di- or tri-nucleated
aromatic ring groups which optionally may be mono- or
poly-substituted, as for example mono-, di- or tri-substituted, as
for example by same or different, in particular same lower alkyl,
as for example C.sub.1-C.sub.8 or C.sub.1-C.sub.4 alkyl groups, and
contain 6 to 20, as for example 6 to 12 ring carbon atoms. Two or
more ring groups may be condensed or, more preferably non-condensed
rings, or two neighboured rings may be linked via a group R
selected from a C--C single bond or an ether (--O--) or an alkylene
bridge, or halogenated alkylene bridge or sulfono group
(--SO.sub.2--). Arylene groups may, for example, be selected from
mono-, di- and tri-nucleated aromatic ring groups, wherein, in the
case of di- and tri-nucleated groups the aromatic rings are
optionally condensed; if said two or three aromatic rings are not
condensed, then they are linked pairwise via a C--C-single bond,
--O--, or an alkylene or halogenated alkylene bridge. As examples
may be mentioned: phenylenes, like hydroquinone; bisphenylenes;
naphthylenes; phenanthrylenes as depicted below:
##STR00002##
wherein R represents a linking group as defined above like --O--,
alkylene, or fluorinated or chlorinated alkylene or a chemical bond
and which may be further substituted as defined above.
[0038] "Alkylene" represents a linear or branched divalent
hydrocarbon group having 1 to 12, 1 to 10, 1 to 8 or 1 to 4 carbon
atoms, in particular example C.sub.1-C.sub.4-alkylene groups, like
--CH.sub.2--, --(CH.sub.2).sub.2--, (CH.sub.2).sub.3--,
--(CH.sub.2).sub.4--, --(CH.sub.2).sub.2--CH(CH.sub.3)--,
--CH.sub.2--CH(CH.sub.3)--CH.sub.2--, (CH.sub.2).sub.4--.
[0039] "Alkyl" represents an residue which is linear or branched
having from 1 to 12, 1 to 10, 1 to 8, 1 to 6 or 1 to 4 carbon
atoms. Examples thereof are: C.sub.1-C.sub.4-alkyl (or "Lower
alkyl") radicals selected from methyl, ethyl, n-propyl, isopropyl,
n-butyl, 2-butyl, isobutyl or tert-butyl, or C.sub.1-C.sub.6-alkyl
radicals selected from C.sub.1-C.sub.4-alkyl radicals as defined
above and additionally pentyl, 1-methylbutyl, 2-methylbutyl,
3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl,
1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl,
2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl,
1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl,
2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl,
1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl,
1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl.
[0040] A "cycloalkyl" group refers to a saturated aliphatic cyclic
hydrocarbon group. The cycloalkyl group has 3-12 carbons, in
particular 3-8 carbons, preferably 3-6 carbons, like 3 carbons. The
cycloalkyl group may be unsubstituted or substituted by one or more
groups selected from halogen, cyano, hydroxy, alkoxy carbonyl,
amido, alkylamido, dialkylamido, nitro, amino, alkylamino,
dialkylamino, carboxyl, thio and thioalkyl. Non-limiting examples
of cycloalkyl group encompass cyclopropyl, cyclobutyl, cyclopentyl,
cyclohexyl, and the like. In another embodiment, the cycloalkyl
comprises 1-4 rings preferably 1 or 2 most preferably 1 ring.
[0041] "Halogen" or "halide" represents F, CI, Br, I.
[0042] "Haloalkyl" represents the above identified "alkyl" groups
substituted by 1 or more, like 1 to 10, in particular 1 to 5,
preferably 1, 2 or 3 identical or different "halogen" residues, in
particular F- or Cl-substituents.
[0043] "Hydroxyl alkyl" represents the above identified "alkyl"
groups substituted by 1 or more, like 1 to 10, in particular 1 to
5, preferably 1, 2 or 3 hydroxyl residues.
[0044] "Thioalkyl" represents the above identified "alkyl" groups
substituted by 1 or more, like 1 to 10, in particular 1 to 5,
preferably 1, 2 or 3 thionly (--SH) residues.
[0045] "Phenyl alkyl" represents the above identified "alkyl"
groups substituted by 1 or 2, preferably 1 phenyl groups.
[0046] "Amino alkyl" represents the above identified "alkyl" groups
substituted by 1 or 2, preferably 1 amino (--NH.sub.2) or
alkylamino (--NH (lower alkyl) or --N(lower alkyl).sub.2)
groups.
[0047] The term "aryl" refers to an aromatic group having at least
one carbocyclic aromatic ring, which may be unsubstituted or
substituted by one or more groups selected from halogen, cyano,
aryl, heteroaryl, haloalkyl, hydroxy, alkoxy carbonyl, amido,
alkylamido, dialkylamido, nitro, amino, alkylamino, dialkylamino,
carboxy or thio or thioalkyl. Nonlimiting examples of aryl rings
are phenyl, naphthyl, and the like. In one embodiment, the aryl
group is a 5-12 membered ring, in particular a 5-8 membered ring,
preferably 5- or 6 membered ring. In one embodiment, the aryl group
is a five membered ring. In one embodiment, the aryl group is a six
membered ring. In another embodiment, the aryl group comprises of
2-4, preferably 2 fused rings.
[0048] The term "arylalkyl" refers to an alkyl group as defined
above substituted by an aryl-group as defined above. Non-limiting
examples of arylalkyl are --CH.sub.2Ph or --CH.sub.2CH.sub.2Ph.
[0049] The term "heteroaryl" refers to an aromatic group having at
least one heterocyclic aromatic ring. In one embodiment, the
heteroaryl comprises at least one heteroatom such as sulfur,
oxygen, nitrogen, silicon, phosphor or any combination thereof, as
part of the ring. In another embodiment, the heteroaryl may be
unsubstituted or substituted by one or more groups selected from
halogen, aryl, heteroaryl, cyano, haloalkyl, hydroxy, alkoxy
carbonyl, amido, alkylamido, dialkylamido, nitro, amino,
alkylamino, dialkylamino, carboxy or thio or thioalkyl. Nonlimiting
examples of heteroaryl rings are pyranyl, pyrrolyl, pyrazinyl,
pyrimidinyl, pyrazolyl, pyridinyl, furanyl, thiophenyl, thiazolyl,
indolyl, imidazolyl, isoxazolyl, and the like. In one embodiment,
the heteroaryl group is a 5-12 membered ring, in particular a 5-8
membered ring preferably a 5- or 6-membered ring. In one
embodiment, the heteroaryl group is a five membered ring. In one
embodiment, the heteroaryl group is a six membered ring. In another
embodiment, the heteroaryl group comprises of 2-4, in particular
2fused rings. In one embodiment, the heteroaryl group is
1,2,3-triazole. In one embodiment the heteroaryl is a pyridyl. In
one embodiment the heteroaryl is a bipyridyl. In one embodiment the
heteroaryl is a terpyridyl.
[0050] A "heterocyclic" group refers to a saturated or mono- or
poly-unsaturated heterocycle. In one embodiment, said heterocycle
refers to a ring structure comprising in addition to carbon atoms,
sulfur, oxygen, nitrogen, silicon or phosphoror any combination
thereof, as part of the ring. In another embodiment the heterocycle
is a 3-12 membered ring, in particular a 4-8 membered ring.
preferably a 5-7 membered ring. In another embodiment the
heterocycle is a 6 membered ring. In another embodiment, the
heterocycle group may be unsubstituted or substituted by a halide,
haloalkyl, hydroxyl, alkoxy, carbonyl, amido, alkylamido,
dialkylamido, cyano, nitro, CO.sub.2H, amino, alkylarnino,
dialkylamino, carboxyl, thio and/or thioalkyl. In another
embodiment, the heterocycle ring may be fused to another saturated
or unsaturated cycloalkyl or heterocyclic 3-8 membered ring. In
another embodiment, the heterocyclic ring is a saturated ring. In
another embodiment, the heterocyclic ring is an unsaturated ring.
The term "carbocyclic ring" refers to a saturated or unsaturated
ring composed exclusively of carbon atoms. In one embodiment, the
carbocyclic ring is a 3-12 membered ring, in particular 3-8
membered ring. In one embodiment, the carbocyclic ring is a five
membered ring. In one embodiment, the carbocyclic ring is a six
membered ring. In one embodiment the carbocyclic ring may be
unsubstituted or substituted by one or more groups selected from
halogen, cyano, haloalkyl, hydroxy, alkoxy carbonyl, amido,
alkylamido, dialkylamido, nitro, amino, alkylamino, dialkylamino,
carboxy or thio or thioalkyl. Nonlimiting examples of carbocyclic
ring are benzene, cyclohexane, and the like. In another embodiment,
the carbocyclic ring comprises of 2-4 condensed or non-condensed
rings.
[0051] The term "PP2b" as used herein refers to a group of chemical
compound (5,5'-bis(1-ethylyl-7-polyethylene
glycol-N,N'-bis(ethylpropyl)-perylene-3,4,9,10-tetracarboxylic
diimde)-2,2'-bipyridine) as represented by the herein identified
formula II, wherein the two PEG residues are the same or different,
and wherein the chain length of the PEG residues is in the range of
10 to 25 consecutive ethylene glycol moieties. A particular PP2b
preparation may uniformly consist of chemical compounds each
containing PEG moieties of identical chain length. It may also
consist of mixtures of 2 or more, like 2 or 3, preferably 2
compounds of the formula (II) showing different PEG chain lengths,
which may be further characterized by stating a mean chain length
for the PEG residues.
[0052] "Vinyl" has to be understood broadly and encompasses
polymerizable monovalent residues of the type C.dbd.C--, as for
example H.sub.2C.dbd.CH-- or H.sub.2C.dbd.C(methyl)-.
[0053] "Mn" represents the number-average molecular weight and is
determined in a conventional manner; more particularly, such
figures relate to Mn values determined by relative methods, such as
gel permeation chromatography with THF as the eluent and
polystyrene standards, or absolute methods, such as vapour phase
osmometry using toluene as the solvent.
[0054] "Mw" represents the weight-average molecular weight and is
determined in a conventional manner; more particularly, such
figures relate to Mw values determined by relative methods, such as
gel permeation chromatography with THF as the eluent and
polystyrene standards, or absolute methods, such as light
scattering.
[0055] The "degree of polymerization" usually refers to the
numerical mean degree of polymerization (determination method: gel
permeation chromatography with THF as the eluent and polystyrene
standards; or GC-MS coupling).
B. Particular Embodiments
[0056] The present invention provides the following particular
embodiments: [0057] 1. A nanofiltration composite membrane
comprising, preferably consisting of [0058] a) at least one
polymeric porous substrate layer (S) comprising at least one
substrate layer forming polymer P1, in particular at least one
polyarylene ether polymer, preferably at least one polyether
sulfone (PES) polymer, and [0059] b) at least one porous
self-assembled supramolecular membrane layer (F) comprising,
preferably essentially consisting of, at least one self-assembled
perylene diimide deposited on said at least one substrate layer
(S).
[0060] Preferably said at least one porous substrate layer (S) has
a mean pore size in the range of less than 450 or less than 300 nm,
in particular 10 to 150, more particular 10 to 100, most preferably
10 to 50 nm.
[0061] Preferably said layer (F) is deposited by passing through
said porous substrate layer (S) a solution of at least one
self-assembling perylene diimide in an aqueous solvent, which
contains an organic co-solvent, like in particular THF, in a
proportion of more than 0.75 Vol.-%, based on the total volume of
the solution, and, more preferably, in a proportion of 1 Vol.-% or
more, based on the total volume of the solution.
[0062] In another particular embodiment said solution contains the
organic co-solvent, like in particular THF, in a proportion of 2
Vol.-% or more, based on the total volume of the solution.
[0063] In another preferred embodiment said aqueous solution
contains THF as organic cosolvent in a proportion of up to 30
Vol.-%, more particularly in a proportion in a range of 1, 2, 3, 4
or 5 to 30 Vol.-%, preferably 2 to 12 Vol.-%, based on the total
volume of the solution.
[0064] By adjusting the content of the organic co-solvent the size
of the supramolecular structure is adjusted to a value just large
enough in order to allow deposition of the membrane building blocks
on said substrate layer (S).
[0065] "Deposited on" in this context, particularly refers to a
reversible deposition of the perylene diimide material on the
substrate immobilized on the substrate by non-covalent, as for
example ionic, hydrophobic and/or dipolar interaction.
[0066] Optionally the thus formed layer (F) may be further subject
o a post-deposition treatment by applying an aqueous alkanolic
solvent, as described herein below. [0067] 2. The composite
membrane of embodiment 1, wherein said composite membrane is
further characterized by at least one of the following ion
retention parameters: [0068] i) Pb.sup.2+ retention of at least 5%,
in particular at least 7%, preferably at least 10%, preferably in a
standardized filtration assay as defined herein below, [0069] ii)
PO.sub.4.sup.3- retention of at least 10%, in particular at least
20% preferably at least 40%, preferably in a standardized
filtration assay as defined herein below.
[0070] "Retention" in this context defines: [0071] a) in one
embodiment, if measured by cross-flow filtration, the increase in
concentration (in % based on the initial concentration in the
liquid medium to be filtered) of a particular ion observed in the
retentate of a liquid medium filtered through a composite membrane
of the invention; and/or [0072] b) in another embodiment, if
measured by dead-end filtration, the concentration (in %) of a
particular ion that is missing to 100%, as deduced by subtraction
of the concentration (in %) of that particular ion observed in the
eluate of a liquid medium filtered through a composite membrane of
the invention.
[0073] If not otherwise stated definition b) preferably applies.
[0074] 3. The composite membrane of embodiment 1 or 2, further
characterized by a flux in the range of 10 to 80 L/m.sup.2/bar/h,
preferably 20 to 50 L/m.sup.2/bar/h, as determined under
standardized conditions. [0075] 4. The composite membrane of one of
the preceding embodiments, wherein said at least one self-assembled
supramolecular membrane layer (F) is non-covalently attached on
said at least one substrate layer (S), as for example by ionic,
hydrophobic and/or dipolar interaction. [0076] 5. The composite
membrane of one of the preceding embodiments, wherein said at least
one self-assembled supramolecular membrane layer (F) has a mean
pore size in the range of 0.001 to 0.01 .mu.m (1 to 10 nm),
preferably 2 to 5 nm. [0077] 6. The composite membrane of
embodiment 3, wherein said at least one self-assembled
supramolecular membrane layer (F) has a pore size distribution
which allows the separation of multivalent inorganic cations, in
particular multivalent metal cations, multivalent inorganic anions,
in particular phosphate anions, and/or organic molecules of molar
mass between 100 and 100,000 g/mol, preferably between 1000 and
10,000 g/mol., dissolved in an aqueous medium. [0078] 7. The
composite membrane of one of the preceding embodiments, wherein
said at least one porous substrate layer (S) has a mean pore size
in the range of 10 to 1000 nm, preferably less than 450 or less
than 300 nm, in particular 10 to 150, more particular 10 to 100,
most preferably 10 to 50 nm. [0079] 8. The composite membrane of
one of the preceding embodiments, wherein said at least one
self-assembled perylene diimide, comprises a perylene diimide of
the following general Formula I or a salt or metal complex
thereof:
##STR00003##
[0079] wherein [0080] R.sub.1 and R.sub.1' are each independently
[(CH.sub.2).sub.qO].sub.rCH.sub.3, [(CH.sub.2).sub.qO].sub.rH
[(CH.sub.2).sub.qC(O)O].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)NH].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.ident.CH].sub.rCH.sub.3,
[(CH.sub.2).sub.qNH].sub.rCH.sub.3,
[(alkylene).sub.qO].sub.rCH.sub.3,
[(alkylene).sub.qC(O)O].sub.rCH.sub.3,
[(alkylene).sub.qC(O)NH].sub.rCH.sub.3,
[(alkylene).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(alkylene).sub.qCH.ident.CH].sub.rCH.sub.3,
[(alkylene).sub.qNH].sub.rCH.sub.3, (C.sub.1-C.sub.32)alkyl,
(C.sub.3-C.sub.8)cycloalkyl, aryl, heteroaryl, chiral group,
(C.sub.1-C.sub.32)alkyl-COOH, (C.sub.1-C.sub.32)alkyl-Si--A, or
[C(O)CHR.sub.3NH].sub.pH wherein said aryl or heteroaryl groups are
optionally substituted by 1-3 groups comprising halide, CN,
CO.sub.2H, OH, SH, NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl) or
O-(C.sub.1-C.sub.6 alkyl); wherein A comprises three same or
different of the following substituents Cl, Br, I,
O-(C.sub.1-C.sub.8)alkyl or (C.sub.1-C.sub.8)alkyl; and wherein
R.sub.3 in said [C(O)CHR.sub.3NH]pH is an alkyl, haloalkyl,
hydroxyalkyl, hydroxyl, aryl, phenyl, phenylalkyl, aminoalkyl and
independently the same or different when p is larger than 1; [0081]
R.sub.2 and R.sub.2' are each independently
[(CH.sub.2).sub.qO].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)O].sub.rCH.sub.3,
[(CH.sub.2).sub.qC(O)NH].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(CH.sub.2).sub.qCH.ident.CH].sub.rCH.sub.3,
[(CH.sub.2).sub.qNH].sub.rCH.sub.3,
[(alkylene).sub.qO].sub.rCH.sub.3,
[(alkylene).sub.qC(O)O].sub.rCH.sub.3,
[(alkylene).sub.qC(O)NH].sub.r(CH.sub.3,
[(alkylene).sub.qCH.sub.2.dbd.CH.sub.2].sub.rCH.sub.3,
[(alkylene).sub.qCH.ident.CH].sub.rCH.sub.3,
[(alkylene).sub.qNH].sub.rCH.sub.3, (C.sub.1-C.sub.32)alkyl,
(C.sub.3-C.sub.8)cycloalkyl, aryl, heteroaryl, chiral group,
(C.sub.1-C.sub.32)alkyl-COOH, (C.sub.1-C.sub.32)alkyl-Si--A, or
[C(O)CHR.sub.4NH].sub.sH wherein said aryl or heteroaryl groups are
optionallysubstituted by 1-3 groups comprising halide, CN,
CO.sub.2H, OH, SH, NH.sub.2, CO.sub.2-(C.sub.1-C.sub.6 alkyl)or
O-(C.sub.1-C.sub.6 alkyl); wherein A comprises three same or
different of the followingsubstituents Cl, Br, I,
O(C.sub.1-C.sub.8)alkyl or C.sub.1-C.sub.8)alkyl; and wherein
R.sub.4 in said [C(O)CHR.sub.4NH].sub.sH is an alkyl, haloalkyl,
hydroxyalkyl, hydroxyl, aryl, phenyl, phenylalkyl, aminoalkyl and
independently the same or different when s is larger than 1; [0082]
R.sub.5 and R.sub.5' are each independently H, --OR.sub.x where
R.sub.x is C.sub.1-C.sub.6 alkyl, [(CH.sub.2).sub.nO].sub.oCH.sub.3
or [(CH.sub.2).sub.nO].sub.oH;
[(CH.sub.2).sub.nC(O)O].sub.oCH.sub.3,
[(CH.sub.2).sub.nC(O)NH].sub.oCH.sub.3,
[(CH.sub.2).sub.nCH.sub.2.dbd.CH.sub.2].sub.oCH.sub.3,
[(CH.sub.2).sub.nCH.ident.CH].sub.oCH.sub.3,
[(CH.sub.2).sub.nNH].sub.oCH.sub.3,
[(alkylene).sub.nO].sub.oCH.sub.3,
[(alkylene).sub.nC(O).sub.o]CH.sub.3,
[(alkylene).sub.nC(O)NH].sub.oCH.sub.3,
[(alkylene).sub.nCH.sub.2.dbd.CH.sub.2].sub.oCH.sub.3,
[(alkylene).sub.nCH.ident.CH].sub.oCH.sub.3,
[(alkylene).sub.nNH].sub.oCH.sub.3, aryl, heteroaryl,
C.ident.C-R.sub.7, CH.dbd.CR.sub.8R.sub.9, NR.sub.10R.sub.11,
chiral group, amino acid, peptide or a saturated carbocyclic or
heterocyclic ring wherein said saturated heterocyclic ring or
heteroaryl contains at least one nitrogen atom and R.sub.5 or
R.sub.5' are connected via the nitrogen atom and wherein said
saturated carbocyclic ring, heterocyclic ring, aryl and heteroaryl
groups are optionally substituted by 1-3 groups comprising halide,
aryl, heteroaryl, CN, CO.sub.2H, OH, SH, NH.sub.2,
CO.sub.2-(C.sub.1-C.sub.6 alkyl) or O-C.sub.1-C.sub.6 alkyl);
[0083] R.sub.7 is H, halo, C.sub.1-C.sub.32)alkyl, aryl, NH.sub.2,
alkyl-amino, COOH, C(O)H, alkyl-COOH heteroaryl, Si(H).sub.3 or
Si[C.sub.1-C.sub.8)alkyl].sub.3 wherein said aryl or heteroaryl
groups are optionally substituted by 1-3 groups comprising halide,
aryl, heteroaryl, CN, CO.sub.2H, OH, SH, NH.sub.2,
CO.sub.2-C.sub.1-C.sub.6 alkyl) or O-C.sub.1-C.sub.6 alkyl);
R.sub.8, R.sub.9, R.sub.10 and R.sub.11 are each independently H,
C.sub.1-C.sub.32)alkyl, aryl, NH.sub.2, alkylamino, COOH, C(O)H,
alkyl-COOH or heteroaryl wherein said aryl or heteroaryl groups are
optionally substituted by 1-3 groups comprising halide, CN,
CO.sub.2H, OH, SH, NH.sub.2, CO.sub.2-C.sub.1-C.sub.6 alkyl) or
O-C.sub.1-C.sub.6 alkyl); [0084] L is a linker; [0085] n is an
integer from 1-5; [0086] o is an integer from 1-100;
[0087] p is an integer from 1-100; [0088] q is an integer from 1-5;
[0089] r is an integer from 1-100; and [0090] s is an integer from
1-100; [0091] wherein if R.sub.5 and/or R.sub.5' are chiral; said
membrane will form a chiral membrane. [0092] 9. The composite
membrane of one of the preceding embodiments, wherein in compounds
of formula I [0093] L is selected from linkers of the formulae (a)
to (f),
##STR00004##
[0093] preferably (e) or (f) [0094] R1 and R1' are each
independently (C.sub.1-C.sub.32)alkyl, preferably
(C.sub.3-C.sub.10)alkyl, [0095] R2 and R2' are each independently
(C.sub.1-C.sub.32)alkyl, preferably (C.sub.3-C.sub.10)alkyl, [0096]
R5 and R5' are each independently [(CH.sub.2).sub.nO].sub.oCH.sub.3
or [(CH.sub.2).sub.nO].sub.oH; [0097] n is an integer from 1-5,
preferably 2 or 3; and [0098] o is an integer from 5-50, preferably
5 to 35. [0099] 10. The composite membrane of one of the preceding
embodiments, wherein said perylene diimide is of the Formula
II:
##STR00005##
[0099] wherein PEG represents a polyethylene glycol residue
comprising 10 to 25 consecutive ethylene glycol units (PEG10 to
PEG25), or a mixture of at least two of said compounds, in
particular a mixture, of a PEG13- and a PEG17-perylene diimide;
wherein the mixing ratio of said two different PEG perylene diimdes
is in the range of 1:100 to 100:1, preferably 1:20 to 20:1. [0100]
Non-limiting examples of suitable mixtures are [0101] 5% PP2b PEG
13+95% PP2b PEG 17 and [0102] 95% PP2b PEG 13+5% PP2b PEG 23 (wt.-%
each) [0103] 11. The composite membrane of one of the preceding
embodiments, wherein at least one porous substrate layer (S) is a
polyarylene ether based, in particular polyethersulfone-based
layer. [0104] 12. The composite membrane of embodiment 11, wherein
said porous substrate layer (S) comprises a polyarylene ether-based
polymer (P1) comprising a repeating unit of formula (Ill)
##STR00006##
[0104] wherein [0105] t and q each independently are 0, 1, 2 or 3,
[0106] Ar and Ar.sup.1 each independently are an arylene group;
[0107] Q, T and Y each independently are a chemical bond or a group
selected from --O--, --S--, --SO.sub.2--, S.dbd.O, C.dbd.O,
--N.dbd.N--, --CR.sub.aR.sub.b-- wherein R.sub.a and R.sub.b are
each independently a hydrogen atom or a C.sub.1-C.sub.12-alkyl,
C.sub.1-C.sub.12-alkoxy or C.sub.6-C.sub.18-aryl group, or wherein
--CR.sub.aR.sub.b-- also may form a 1,1-cycloalkylidene group; and
wherein at least one of Q, T and Y is not --O--. Preferably at
least one of Q, T and Y is --SO.sub.2--. [0108] 13. The composite
membrane of one of the preceding embodiments, wherein said polymer
(P1), in particular said polyethersulfone-based polymer, has a Mw
in the range of 50.000 to 150.000, in particular 70.000 to 100.000
g/mol, as determined by Gel Permeation Chromatography (GPC) in
N-dimethylacetamide (DMAc). [0109] 14. The composite membrane of
one of the preceding embodiments, wherein the membrane layer (F)
deposited on top of the substrate layer (S) has a layer thickness
in the range of at least 0.1 g/m.sup.2 (mass of (F) per area of
(S)), like 0.1 to 10 g/m.sup.2 preferably 1 to 6, most preferably 2
to 4 g/m.sup.2. [0110] 15. The composite membrane of one of the
preceding embodiments, a) in the form of a flat sheet, or b) in the
form of a multibore hollow fibre.
[0111] In one particular embodiment of the invention, composite
membranes are present as spiral wound membranes, as pillows or flat
sheet membranes.
[0112] In another embodiment of the invention, composite membranes
are present as tubular membranes.
[0113] In another embodiment of the invention, composite membranes
are present as hollow fiber membranes or capillaries.
[0114] In yet another embodiment of the invention, composite
membranes are present as single bore hollow fiber membranes.
[0115] In yet another, preferred embodiment of the invention,
composite membranes are present as multibore hollow fiber
membranes.
[0116] Multiple channel membranes, also referred to as multibore
membranes, comprise more than one longitudinal channels also
referred to simply as "channels".
[0117] In a preferred embodiment, the number of channels is
typically 2 to 19. In one embodiment, multiple channel membranes
comprise two or three channels. In another embodiment, multiple
channel membranes comprise 5 to 9 channels. In one preferred
embodiment, multiple channel membranes comprise seven channels.
[0118] In another embodiment the number of channels is 20 to
100.
[0119] The shape of such channels, also referred to as "bores", may
vary. In one embodiment, such channels have an essentially circular
diameter. In another embodiment, such channels have an essentially
ellipsoid diameter. In yet another embodiment, channels have an
essentially rectangular diameter. In some cases, the actual form of
such channels may deviate from the idealized circular, ellipsoid or
rectangular form.
[0120] Normally, such channels have a diameter (for essentially
circular diameters), smaller diameter (for essentially ellipsoid
diameters) or smaller feed size (for essentially rectangular
diameters) of 0.05 mm to 3 mm, preferably 0.5 to 2 mm, more
preferably 0.9 to 1.5 mm. In another preferred embodiment, such
channels have a diameter (for essentially circular diameters),
smaller diameter (for essentially ellipsoid diameters) or smaller
feed size (for essentially rectangular diameters) in the range from
0.2 to 0.9 mm.
[0121] For channels with an essentially rectangular shape, these
channels can be arranged in a row.
[0122] For channels with an essentially circular shape, these
channels are in a preferred embodiment arranged such that a central
channel is surrounded by the other channels. In one preferred
embodiment, a membrane comprises one central channel and for
example 4, 6 or 18 further channels arranged cyclically around the
central channel.
[0123] The wall thickness in such multiple channel membranes is
normally from 0.02 to 1 mm at the thinnest position, preferably 30
to 500 .mu.m, more preferably 100 to 300 .mu.m.
[0124] Normally, such multiple channel membranes according to the
invention have an essentially circular, ellipsoid or rectangular
diameter. Preferably, such multiple channel membranes according to
the invention are essentially circular. In one preferred
embodiment, such multiple channel membranes according to the
invention have a diameter (for essentially circular diameters),
smaller diameter (for essentially ellipsoid diameters) or smaller
feed size (for essentially rectangular diameters) of 2 to 10 mm,
preferably 3 to 8 mm, more preferably 4 to 6 mm. In another
preferred embodiment, such multiple channel membranes according to
the invention have a diameter (for essentially circular diameters),
smaller diameter (for essentially ellipsoid diameters) or smaller
feed size (for essentially rectangular diameters) of 2 to 4 mm.
[0125] In one embodiment the rejection layer is located on the
inside of each channel of said multiple channel membrane. [0126]
16. The composite membrane of one of the preceding embodiments, in
the form of a) a flat sheet or b) in tubular form, wherein the
self-assembled supramolecular membrane layer (F) is deposited on
the inner surface of the tubular substrate (S). [0127] 17. A method
of preparing a composite membrane of any one of the preceding
embodiments, which method comprises [0128] a) providing at least
one porous substrate layer (S), preferably comprising at least one
polymer (P1), preferably polyarylene ether, more preferably PES
polymer [0129] b) providing a solution of at least one
self-assembling perylene diimide in an aqueous solvent containing
an organic co-solvent, preferably THF, in a proportion suitable for
reducing the molecular weight of the supramolecular perylene
diimide structures; [0130] c) passing said solution of step b)
through the porous substrate layer of step a), thereby depositing
said at least one self-assembled perylene diimide from said
solution onto said substrate layer (S) to form at least one porous
self-assembled supramolecular membrane (F), optionally followed by
washing the deposited membrane with an aqueous liquid, preferably
water, and preferably maintaining said membrane in said aqueous
liquid; and [0131] e) optionally repeating steps b) and c) with the
same solution or a solution with different, preferably higher,
proportion of an organic, preferably the same, cosolvent. [0132]
18. The method of embodiment 17, wherein in step b) a solution of
at least one self-assembling perylene diimide in an aqueous solvent
is applied, which contains said said organic co-solvent in an
amount sufficient to increase the proportion of lower molecular
weight supramolecular fibrils with a molecular mass in the range of
10.000 to 1.000.000 g/mol to a value in the range of 10% to 100%,
in particular 15% to 60%. [0133] 19. The method of anyone of the
embodiments 17 to 18, wherein in step b) a solution of at least one
self-assembling perylene diimide in an aqueous solvent is applied,
which contains THF as said organic co-solvent in a proportion of
more than 0,75 Vol.-%, in particular in a range of 1 to 30 Vol.-%,
preferably 1, 2, 3, 4 or 5 to 15 Vol.-%, more preferably in a range
of 2 to 12 Vol.-%, based on the total volume of the solution.
[0134] 20. The method of anyone of the embodiments 17 to 19,
wherein additionally d) the at least one deposited porous
self-assembled supramolecular membrane (F) is subjected to a
post-deposition treatment by applying (for example by incubating
with and/or passing through, preferably by passing through at
pressures below 5 bar) an aqueous-alkanolic solvent, in particular
a water/ethanol mixture having an ethanol content in a proportion
of 25 to 75 Vol.-%, based on the total volume of the solvent
mixture, to said deposited membrane.
[0135] As illustrated in the subsequent experimental section, in
particular Tables 2, 3 and 6, said post-deposition treatment
(densification) results in a systematic increase of retention of
the obtained membrane structure. [0136] 21. A method of
separation/filtration/purification of metal cations, in particular
multivalent metal cations, or heavy metal cations, in particular
multivalent heavy metal cations, as for example multivalent ions of
Ni, Cr, Zn, Pb, Gd, Ca, and/ or inorganic anions, in particular
phosphate ions, which method comprises passing an aqueous medium
containing at least one of said ions through a nanofiltration
composite membrane as defined in one of the embodiments 1 to 16 or
prepared by a method of one of the embodiments 17 to 20, thereby
obtaining an aqueous filtrate depleted from at least one of said
ions and a retentate enriched with at least one of said ions.
[0137] If not otherwise defined, the term "metal cations"
encompasses any metal cation of any metal selected from the groups
1 to 16, in particular groups 2 to 14 (IUPAC 1985) of the periodic
system of chemical elements.
[0138] If not otherwise defined, the term "heavy metal cations"
encompasses any cation derived from a metal having a density of
more than 5.0 g/cm.sup.3.
[0139] If not otherwise defined, the term "inorganic anions",
defines any inorganic anion, in particular oxidic anions, of a
post-transition metal (like Al, Ga, In, TI, Sn, Pb, Bi, Po),
metalloid (like Si, Ge, As, Sb, Te, At) or non-metal (like P, S,
Se, N, CI, Br, I) element of groups 13 to 17, in particular groups
14 to 16 (IUPAC 1985) of the periodic system of chemical elements.
[0140] 22. The method of embodiment 20 applied in waste water
treatment. [0141] 23. A method of separation/filtration/ of water
soluble organic molecules (like dyes, like methylene blue) which
method comprises passing an aqueous medium containing at least one
of said organic molecules through a nanofiltration composite
membrane as defined in one of the embodiments 1 to 16 or prepared
by a method of one of the embodiments 17 to 20, thereby obtaining
an aqueous filtrate depleted from at least one dye and a retentate
enriched with at least one of said dye. [0142] 24. The method of
one of the embodiments 17 to 20 performed with a nanofiltration
composite membrane in the form of a flat sheet or in tubular form
or in multi-bore tubular form. [0143] 25. A filter cartridge
comprising at least one composite membrane of one of the preceding
embodiments 1 to 16, in the form of a) a flat sheet or b) in
tubular form, wherein the self-assembled supramolecular membrane
layer (F) is deposited on the inner surface of the tubular
substrates (S). [0144] 26. A filtration device comprising at least
one filter cartridge of embodiment 25. [0145] 27. The method or
device or cartridge of anyone of the embodiments 21 to 26, wherein
the composite membrane as applied therein is characterized by a
permeance 1 to 200 L/m.sup.2/h/bar, preferably 10 to 50
L/m.sup.2/h/bar.
[0146] "Passing through" as used herein encompasses both cross-flow
and dead-end flow methods.
C. Further Embodiments of the Invention
1. Preparation of Membrane Substrate Layer (S)
[0147] The manufacture of membranes such as NF membranes and their
use in filtration modules of different configuration is known in
the art. See for example M C Porter et al. in Handbook of
Industrial Membrane Technology (William Andrew Publishing/Noyes,
1990).
1.1 General
[0148] The at least one substrate or carrier layer (S) as used in
the composite membranes of the invention, are in principle of a
type which is well known in the art or may be prepared by applying
well-known techniques of substrate layer formation
[0149] As the main component an organic polymer (P1) is applied for
preparing the layer (S).
[0150] Suitable polymers (P1) applicable for this purpose are well
known in the art. In particular, there may be mentioned
polyarylenes ether, polysulfones (PSU), polyethersulfones (PESU),
polyphenylenesulfones (PPSU), polyamides (PA), polyvinylalcohols
(PVA), cellulose acetates (CA), cellulose triacetates (CTA),
CA-triacetate blends, cellulose ester, cellulose nitrates,
regenerated cellulose, aromatic, aromatic/aliphatic or aliphatic
polyamides, aromatic, aromatic/aliphatic or aliphatic polyimides,
polybenzimidazoles (PBI), polybenzimidazolones (PBIL),
polyacrylonitrils (PAN), PAN-poly(vinyl chloride) copolymers
(PAN-PVC), PAN-methallyl sulfonate copolymers,
poly(dimethylphenylene oxide) (PPO), polycarbonates, polyesters,
polytetrafluroethylenes (PTFE), poly(vinylidene fluorides) (PVDF),
polystyrenes, polypropylenes (PP), polyelectrolyte complexes,
poly(methyl methacrylates) PMMA, polydimethylsiloxanes (PDMS),
aromatic, aromatic/aliphatic or aliphatic polyimidourethanes,
aromatic, aromatic/aliphatic or aliphatic polyamidimides,
crosslinked polyimides or mixtures thereof.
[0151] Preferably substrate or carrier layer(s) (S) comprise as the
main polymer component a polymer selected from polysulfone,
polyethersulfone, PVDF, polyimide, polyamidimide, crosslinked
polyimides, polyimide urethanes, cellulose acetate or mixtures
thereof. Particularly preferred carrier layer(s) (S) comprise as
the main polymer component at least one polyethersulfone,
optionally in admixture with at least one further polymer, selected
from polysulfone, PVDF, polyimide, polyamidimide, crosslinked
polyimides, polyimide urethanes, cellulose acetate or mixtures
thereof. Most preferred carrier layer(s) (S) essentially consist of
one or polyethersulfones as the single main polymer constituent.
Said polymer has to be soluble in suitable organic solvents, such
as N-methylpyrrolidone, in order to form a castable or extrudable
polymer solution from which, upon coagulation a porous membrane
structure may be formed.
[0152] Suitable polymers, in particular polyarylene ethers, more
particular PES polymers, preferably have a mean molecular weight Mn
(number average) in the range from 2.000 to 70.000 g/mol,
especially preferably 5.000 to 40.000 g/mol and particularly
preferably 7.000 to 30.000 g/mol. Preferably such polymers have a
polydispersity (Mw/Mn) from 1.5 to 5, more preferably 2 to 4.
[0153] In one embodiment, substrate or carrier layer(s) (S)
comprise at least one further additive like polyvinylpyrrolidones
(PVP), polyethylene glycols (PEG), amphiphilic block copolymers or
triblock copolymers like PEG- PPO (polypropyleneoxide)-PEG.
[0154] Non-limiting examples of suitable PVPs are [0155]
Luvitec.RTM. K90 Polyvinylpyrrolidone with a solution viscosity
characterized by the K-value of 90, determined according to the
method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58))
[0156] Luvitec.RTM. K30 Polyvinylpyrrolidone with a solution
viscosity characterized by the K-value of 30, determined according
to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932
(58))
[0157] In a preferred embodiment, substrate or carrier layer(s) (S)
comprise as major components polysulfones or polyethersulfone in
combination with polyvinylpyrrolidone as a further additive.
[0158] In one preferred embodiment, substrate or carrier layer(s)
(S) comprise 80 to 50% by weight of polyethersulfone and 20 to
50%by weight of polyvinylpyrrolidone.
[0159] In another embodiment, substrate or carrier layer(s) (S)
comprise 99 to 80% by weight of polyethersulfone and 1 to 20% by
weight of polyvinylpyrrolidone.
[0160] In one preferred embodiment, substrate or carrier layer(s)
(S) comprise 99.9 to 50% by weight of a combination of
polyethersulfone and 0.1 to 50% by weight of
polyvinylpyrrolidone.
[0161] In another embodiment substrate or carrier layer(s) (S)
comprise 95 to 80% by weight of and 5 to 15% by weight of
polyvinylpyrrolidone.
[0162] In another embodiment the substrate or carrier layer(s) (S)
may comprise organic or inorganic particles in the nanometer size
range, such as zeolite particles, in order to increase the membrane
porosity and/or hydrophilicity. This can for example be achieved by
including such nanoparticles in the dope solution for the
preparation of said support layer.
[0163] Suitable substrate or carrier layer(s) (S) are either in the
form of flat sheets, for example in the size range of at least 0.5
cm.sup.2, as for example 0.5 to 50 cm.sup.2; The layer thickness
may be in the range of 0.2 to 10 mm in particular 0.7 to 3 mm.
1.2 Preparation of Sheet-Like Substrate Layer (S)
[0164] In one embodiment the substrate layer is a conventional
sheet like structure.
[0165] Preparation of the sponge-like substrate layer (S) is
performed by applying well-known techniques of membrane formation,
as for example described in C. A. Smolders et al J. Membr. Sci.:
Vol 73, (1992), 259.
[0166] A particular method of preparation is known as phase
separation method.
[0167] In a first step the polymer (P1), as for example the PES
prepared as described herein is dried, as for example at a
temperature in the range of 20 to 80, as for example 60.degree. C.
under vacuum in order to remove excess liquid.
[0168] In a second step a homogeneous dope solution (D) comprising
the polymer (P1) in a suitable solvent system is prepared. Said
solvent system contains at least one solvent selected from
N-methylpyrrolidone (NMP), N-dimethylacetamide (DMAc),
dimethylsulfoxide (DMSO), dimethylformamide (DMF),
triethylphosphate, tetrahydrofuran (THF), 1,4-dioxane, methyl ethyl
ketone (MEK), or a combination thereof; and, additionally may
contain at least one further additive selected from ethylene
glycol, diethylene glycol, polyethylene glycol, glycerol, methanol,
ethanol, isopropanol, polyvinylpyrrolidone, or a combination
thereof, wherein said additive is contained in said polymer
solution in a range of 0-50, like 0-30 wt.-% per total weight of
the polymer solution.
[0169] The polymer content is in the range of 10 to 40, or 16 to 24
wt.-% based on the total weight of the solution.
[0170] In a third step, the polymer solution is then cast on a
solid support, as for example glass plate using a casting knife
suitably of applying a polymer layer of sufficient thickness.
[0171] Immediately afterwards, in a fourth step, the polymer layer
provided on said support is immersed in a coagulant bath,
containing a water-based coagulation liquid, e.g. a tap water
coagulant bath. Optionally, water may be applied in admixture with
at least one lower alcohol as coagulant bath, in particular
methanol, ethanol, isopropanol, and optionally in admixture with at
least one solvent as defined above. The as-cast membranes were
soaked in water for at least 2 days with constant change of water
to ensure complete removal of solvent in order to induce phase
inversion.
[0172] As a result of this procedure a membrane substrate
exhibiting a sponge-like structure is obtained.
[0173] In another embodiment a process for making membrane
substrate layers S comprises the following steps:
[0174] In step a) a dope solution (D) is provided comprising at
least one polymer (P1) and at least one solvent (L)
[0175] In step b), at least coagulant (C) is added to said dope
solution (D). Thereby, said at least one polymer (P1) is coagulated
to obtain membraneS.
[0176] Coagulants (C) have lower solubility of polymer (P1) than
solvent (L). Suitable coagulants.COPYRGT. comprise for example
liquid water, water vapor, alcohols or mixtures thereof. In one
embodiment coagulants (C) are liquid water, water vapor, alcohols
or mixtures thereof.
[0177] Preferably alcohols suitable as coagulants (C) are mono-,
di- or trialkanols bearing no further functional groups. Examples
are iso-propanol, ethylene glycol or propylene glycol.
[0178] In a further embodiment the manufacturing of membranes
substrates S includes non-solvent induced phase separation
(NIPS).
[0179] In said NIPS process, the polymers (P1) used as starting
materials are dissolved in at least one solvent (L) together with
any additive(s) used. In a next step, a porous polymeric membrane
is formed under controlled conditions in a coagulation bath. In
most cases, the coagulation bath contains water as coagulant (C),
or the coagulation bath is an aqueous medium, wherein the matrix
forming polymer is not soluble. The cloud point of the polymer is
defined in the ideal ternary phase diagram. In a bimodal phase
separation, a microscopic porous architecture is then obtained, and
water soluble components (including polymeric additives) are
finally found in the aqueous phase.
[0180] In case further additives like second dope polymers (DP2)
are present that are simultaneously compatible with the coagulant
(C) and the matrix polymer(s), segregation on the surface results.
With the surface segregation, an enrichment of the certain
additives is observed. The membrane surface thus offers new (for
example hydrophilic) properties compared to the primarily
matrix-forming polymer, by said phase separation induced enrichment
of the additive.
[0181] In another embodiment of the invention a typical process for
the preparation of a solution for membrane substrate (S)
preparation is characterized by the following steps: [0182] a1)
Providing a dope solution (D) comprising at least one polymer (P1)
and at least one solvent (L), [0183] a2) Adding further additives
like pore forming additives such as PVP, PEG, sulfonated PESU or
mixtures thereof, [0184] a3) Heating the mixture until a viscous
solution is obtained; typically temperature of the dope solution
(D) is 5-250 .degree. C., preferably 25-150 .degree. C., more
preferably 50-90 .degree. C. [0185] a4) Stirring of the
solution/suspension until a mixture is formed within 1-15 h,
typically the homogenization is finalized within 2 h. [0186] b)
Casting the membrane dope in a coagulation bath to obtain a
membrane structure. Optionally the casting can be done using a
polymeric support (non-woven) for stabilizing the membrane
structure mechanically.
[0187] Optionally processes of membrane layer (S) preparation
according to the invention as described herein above as well as in
the following section can be followed by further process steps. For
example such processes may include c) oxidative treatment of the
membrane (S) previously obtained, for example using sodium
hypochlorite. Such processes are for example described in I. M.
Wienk, E. E. B. Meuleman, Z. Borneman, Th. Van den Boomgaard, C. A.
Smoulders, Chemical Treatment of Membranes of a Polymer Blend:
Mechanism of the reaction of hypochlorite with
poly(vinylpyrrolidone), Journal of Polymer Science: Part A: Polymer
Chemistry 1995, 33, 49-54.
[0188] Processes according to the invention as described herein
above as well as in the following section may further comprise d)
washing of the membrane with water.
1.3 Preparation of Multiple Channel Substrate Layers
[0189] Particularity preferred are substrate or carrier layer(s)
(S) in the form of a multiple channel membrane, either in the form
of a flat (two-dimensional) sheet containing side-by-side arranged
multiple parallel channels in which the active separation layer is
arranged in the channels. Said channels are embedded in a porous
matrix of said polymer material. Said sheets may be wound in the
form of a spiral thus forming a three-dimensional structure.
[0190] Most preferred are cylindrical substrate or carrier layer(s)
(S) in which the active separation layer is arranged in the
channels and which parallel channels are arranged in a bundle
surrounded by the porous polymeric matrix material. Thereby a
significant increase of surface area of the channels relative to
the outer surface area of the cylindrical structure is
obtained.
[0191] Suitable multiple channel membrane carriers can for example
be obtained using extrusion processes as disclosed in U.S. Pat. No.
6,787,216 B1, col. 2, In. 57 to col. 5, In. 58, incorporated herein
by reference. They are also commercially available from Inge GmbH
Germany, and commercialized under the trade name Multibore O. As
examples there may be mentioned:
[0192] "Inge Multibore.RTM. membranes 0.9" with an average diameter
of 0.9 mm per channel and an outer membrane diameter of 4.0 mm.
[0193] "Inge Multibore.RTM. membranes 1.5" with an average diameter
of 1.5 mm per channel and an outer membrane diameter of 6.0 mm.
[0194] In a preferred embodiment the membrane material for the
manufacture of such multiple channel membranes are soluble
thermoplastic polymer. Examples are polysulfones, poly (ether
sulfones), polyvinylidene chloride, polyvinylidene fluoride,
polyvinyl chloride, polyacrylonitrile, etc.
[0195] The polymer is dissolved prior to extrusion in a usual
solvent and additives like PVP, or nanoparticles, can be added. A
usual solvent is N-methylpyrrolidone. Cosolvents may be added, as
for example glycerol.
[0196] The polymer solution is extruded through a extrusion nozzle
with internal hollow needles to form a cylindrical structure
containing the desired number of internal channels. Through said
hollow needles a coagulating agent is injected into the extruded
polymer solution in order to obtain the channels. The outer surface
of the extruded structure is contacted with a coagulation agent in
order to form and stabilize the outer shape of the desired porous
structure.
[0197] Coagulation agents are known to the expert. Many coagulation
agents suitable for the present purpose are non-solvents for the
polymer that are miscible with the solvent as applied for preparing
the polymer solution. The choice for the non-solvent depends on the
polymer and the solvent. A common solvent is N-methylpyrrolidone.
Examples of non-solvents for use with this solvent are
dimethylformamide, dimethyl sulfoxide and water. The skilled reader
can adjust the strength of the coagulation agent by the choice of
the combination solvent/non-solvent and the ratio of
solvent/non-solvent.
[0198] It is also well-known to a person of ordinary skill in the
art, that the pore size of the carrier can be specifically adjusted
by variation of the coagulation conditions (strength of the
coagulation system). In this way it is also possible to generate a
pore size gradient, for example with smaller pores on the active
inner surface of an internal channel, which is in direct contact
with the liquid medium to be treated, and a larger pore size on the
opposite side, as for example the outer surface of the substrate,
like the cylindrical multibore membrane. Suitable techniques for
adjusting the pore size are well known to a skilled reader. The
strength of the coagulation may be adjusted by the combination of
non-solvent(s)/solvent(s) and adapting their ratio. Coagulation
solvent systems are known to the person skilled in the art and can
be adjusted by routine experiments.
[0199] It is also possible to form an additional separating layer
by applying a coating in the channels. Coating materials usual to
that end are known to the expert. A survey of suitable coating
materials is given by Robert J. Petersen in Journal of Membrane
Science 83 , 81-150 (1993). A preferred inner coating is described
in more detail below.
[0200] The diameter of the channels of the multiple channel
membranes of the invention is between 0.1 and 8 mm and preferably
between 0.1 and 6 mm. The thickness of the walls is adjusted to the
pressure to be exerted in the channels depending on the intended
use. In general, the thickness of the walls is between 0.05 and 1.5
mm and preferably between 0.1-0.5 mm. The cylindrical membranes
contain at least four and preferably 7 to 19 channels. The diameter
of the cylindrical membrane generally is between 1 to 20 mm and
preferably between 2 and 10 mm.
1.4. Preparation of PES Polymers
[0201] Unless otherwise stated, preparation of polymers is
generally performed by applying standard methods of polymer
technology. In general, the reagents and monomeric constituents as
used herein are either commercially available or well known from
the prior art or easily accessible to a skilled reader via
disclosure of the prior art.
[0202] In general, the preferred polyarylene ether sulfone (PES)
polymer P1 can be synthesized, for example by reacting a dialkali
metal salt of an aromatic diol and an aromatic dihalide as taught,
for example by R. N. Johnson et al., J. Polym. Sci. A-1, Vol. 5,
2375 (1967).
[0203] Examples of suitable aromatic dihalides (M1) include:
bis(4-chlorophenyl)sulfone, bis(4-fluorophenyl) sulfone,
bis(4-bromophenyl) sulfone, bis(4-iodophenyl) sulfone,
bis(2-chlorophenyl) sulfone, bis(2-fluorophenyl) sulfone, bis
(2-methyl-4-chlorophenyl) sulfone, bis(2-methyl-4-fluorophenyl)
sulfone, bis(3,5-dimethyl-4-chlorophenyl) sulfone,
bis(3,5-dimethyl-4-flurophenyl) sulfone and corresponding lower
alkyl substituted analogs thereof. They may be used either
individually or as a combination of two or more monomeric
constituents thereof. Particular examples of dihalides are
bis(4-chlorophenyl) sulfone (also designated (4,4'-dichlorophenyl)
sulfone; DCDPS) and bis(4-fluorophenyl) sulfone.
[0204] Examples of suitable dihydric aromatic alcohols (M2) which
are to react with the aromatic dihalide are: hydroquinone,
resorcinol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene,
1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 4,4'-bisphenol,
2,2'-bisphenol, bis(4-hydroxyphenyl) ether, bis(2-hydroxyphenyl)
ether, 2,2-bis(4-hydroxyphenyl)propane,
2,2-bis(3-methyl-4-hydroxy-phenyl)propane,
2,2-bis(3,5-dimethyl-4-hydroyphenyl)propane,
bis(4-hydroxyphenyl)methane, and
2,2-bis(3,5-dimethyl-4-hydroxypenyl)hexafluoropropane. Preferred of
them are hydroquinone, resorcinol, 1,5-dihydroxynaphthalene,
1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,
2,7-dihydroxynaphthalene, 4,4'-biphenol, bis(4-hydroxyphenyl)
ether, and bis(2-hydroxyphenyl) ether. They may be used either
individually or as a combination of two or more monomeric
constituents M2a. Particular examples of such dihydric aromatic
alcohols are 4,4'-bisphenol and 2,2'-bisphenol.
[0205] The dialkali metal salt of said dihydric aromatic phenol is
obtainable by the reaction between the dihydric aromatic alcohol
and an alkali metal compound, such as potassium carbonate,
potassium hydroxide, sodium carbonate or sodium hydroxide.
[0206] The reaction between the dihydric aromatic alcohol dialkali
metal salt and the aromatic dihalide is carried out as described in
the art (see for example [Harrison et al, Polymer preprints (2000)
41 (2) 1239).] Harrison et al, Polymer preprints (2000) 41 (2)
1239).
[0207] For example a in a polar solvent such as dimethyl sulfoxide,
sulfolane, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,
N,N-dimethylformamide, N,N-dimethylacetamide, and diphenyl sulfone,
or mixtures thereof or mixtures of such polar solvents with apolar
organic solvents like toluene may be applied.
[0208] The reaction temperature is typically in the range of 140 to
320.degree. C., preferentially 160 to 250.degree. C. The reaction
time may be in the range of 0.5 to 100 h, preferentially 2 to 15
h.
[0209] The use of either one of the dihydric aromatic alcohol
alkali metal salt and the aromatic dihalide in excess results in
the formation of end groups that can be utilized for molecular
weight control. Otherwise, if the two constituents are used in
equimolar amounts, and either one of a monohydric phenol, as for
example, phenol, cresol, 4-phenylphenol or 3-phenylphenol, and an
aromatic halide, as for example 4-chlorophenyl sulfone,
1-chloro-4-nitrobenzene, 1-chloro-2-nitrobenzene,
1-chloro-3-nitrobenzene, 4-fluorobenzophenone,
1-fluoro-4-nitrobenzene, 1-fluoro-2-nitrobenzene or
1-fluoro-3-nitrobenzene is added for chain termination.
[0210] Non-limiting examples of suitable repeating units of the
general formula III are as follows:
##STR00007## ##STR00008## ##STR00009##
[0211] In addition to the units (1) to (16) preference is also
given to those units in which one or more 1,4-dihydroxyphenyl units
are replaced by resorcinol or dihydroxynaphthalene units.
[0212] Particularly preferred units of the general formula (III)
are units (9), (15) and (16). It is also particularly preferred
when the polyarylene ether blocks are formed essentially from one
kind of units of the general formula (III), especially from one
unit selected from (9), (15) and (16).
[0213] The degree of polymerization (calculated on the basis of
repeating units composed of one monomer (M1) and one monomer (M2),
of the thus obtained polymer may be in the range of 40 to 120, in
particular 50 to 80 or 55 to 75.
2. Preparation of a NF Composite Membrane Carrying a Supramolecular
Separation Layer (F)
[0214] For preparing a composite membrane suitable for NF
applications, the substrate (S) is further modified by depositing a
self-assembled supramolecular active layer (F) onto its surface.
For this purpose commercially available porous
polyethersulfone-based membrane substrate layer (S) of different
geometry (flat sheets, hollow fibres) may be applied.
[0215] Care has to be taken that substrate membranes of proper pore
size are chosen, the pore size should be such that the
supramolecular fibrils of the self-assembling material are retained
on the surface of the substrate and do not pass through.
[0216] The preparation of a composite membrane of the invention
comprises the following steps [0217] a) providing a porous
substrate membrane layer (S) of suitable pore size, [0218] b)
providing a solution of at least one self-assembling perylene
diimide in an aqueous solvent containing an organic co-solvent, as
for example a dipolar aprotic solvent, like THF, in a proportion
suitable for reducing the molecular weight of the supramolecular
perylene diimide structures, as for example in a proportion of 0.5
to 30 or 1 to 15 Vol.-%; [0219] c) passing said solution of step b)
through the porous substrate layer (S) of step a), thereby
depositing said at least one self-assembled perylene diimide from
said solution onto said substrate layer (S) to form a porous
self-assembled supramolecular membrane (F), optionally followed by
washing the deposited membrane with an aqueous liquid, preferably
water, and preferably maintaining said membrane in said aqueous
liquid; and optionally repeating steps b) and c) with the same
solution or a solution with different, preferably higher,
proportion of an organic, preferably the same, co-solvent; and
[0220] d) optionally the deposited porous self-assembled
supramolecular membrane (F) is subjected to a post-deposition
treatment by applying an aqueous-alkanolic solvent, in particular a
water/ethanol mixture having an ethanol content in a proportion of
25 to 75 Vol.-% to said deposited membrane.
[0221] More particularly the perylene diimide, like PP2b is
dissolved at a suitable temperature, like ambient temperature, in
the organic solvent, like in particular THF. Then a mixture of
water and THF is added to the solution at room temperature in a
proportion to adjust the intended final concentration of the
organic solvent.
[0222] This solution is then pumped through said substrate layer by
adjusting a suitable water flux, depending on the pore size and
size of the membrane material (S), for example in the range of 0.05
to 1 mL/min/0.7 cm.sup.2' or 0.5 to 10 L/m.sup.2/h through said
membrane. For example the substrate layer may be a flat sheet
membrane mounted in conventional filter housing. Two or more
identical or different layers may be deposited on a flat sheet in
the same manner by repeating the deposition procedure.
[0223] To deposit the perylene diimide, like PP2b, at the inner
side of hollow bores, for example of a conventional INGE
mulitbore.RTM. systrem, the permeate flow thereof is reduced to
zero, and the PP2b solution in the desired water/THF mixture is
flushed through the bores (feed flow=retentate flow; permeate
flow=0), until the liquid volume inside the bores is exchanged at
least twice. Then, the flows are switched to deposition (feed
flow=permeate flow; retentate flow=0). The PP2b solution is thus
deposited onto the inner side of the bores. The pump speed may be
for example in the range of 0.1 to 5 mL/min per 10 cm per multibore
strand. Two or more identical or different layers may be deposited
in the same manner deposited,
[0224] In order to obtain improved retention of multivalent ions
and dissolved organic matter, an already deposited PP2b structure
may be partially dissolved in order to reduce the sizes of the
self-assembled structures of PP2b after deposition.
[0225] For this purpose a densification treatment may be performed
with an alkanol/water mixture, as for example an ethanol/water
mixture of appropriate mixing ratio, as for example 1:2 to 2:1, in
particular with an 1:1 EtOH:H.sub.2O solution. The membrane
structure is flushed with said solution until the intended degree
of densification is obtained Subsequently the obtained densified
membrane is flushed with water.
Experimental Part
Materials:
[0226] PP2b ((5,5'-bis(1-ethylyl-7-polyethylene
glycol-N,N'-bis(ethylpropyl)-perylene-3,4,9,10-tetracarboxylic
diimde)-2,2'-bipyridine) as used in the following examples is
represented by the above-mentioned formula II and was synthesized
according to the teaching of WO2012/025928, in particular Example
3. The average chain length of the polyethylene glycol side chains
was adjusted to 17.
[0227] PES membrane of the type NADIR UP150, specified with a
nominal molecular-weight-cut-off at 150 kDa, was cut to circular
flat sheets with an effective area of 0.7 cm.sup.2.
[0228] "Inge Multibore.RTM. membranes 0.9" with an average diameter
of 0.9 mm per channel and an outer membrane diameter of 4.0 mm.
[0229] "Inge Multibore.RTM. membranes 1.5" with an average diameter
of 1.5 mm per channel and an outer membrane diameter of 6.0 mm.
Methods:
a) Determination of Permeance
[0230] All experiments were performed at ambient conditions. The
membranes were flushed by de-ionized water at a controlled flux of
0.1 mL/min. By measuring the overpressure before the membrane, the
gravimetrically determined mass of eluted water over at least 10
minutes, and knowing the density of water and the area of the
membrane, the permeance in units of L/m.sup.2/h/bar is calculated.
The density of water is assumed to be 0.997 g/mL for this
purpose.
b) Determination of Ion Retention:
[0231] In general, analytical methods of established in water
analytics may be applied for the measurement of ions like Pb.sup.2+
and (PO.sub.4).sup.3-. See for example Rolf Pohling, Chemische
Reaktionen in der Wasseranalyse, Springer Verlag Berlin Heidelberg
2015.
Method for Determination of Pb.sup.2+ Ion Retention:
[0232] A solution of 50 ppm Pb(NO.sub.3).sub.2 was prepared in
de-ionized water. 10 ml of this Pb(NO.sub.3).sub.2 solution were
added into the permeation cell (diameter 45 mm), which is then
pressurized (2 bar) until 3 mL were eluted, then 5 mL (still 2 bar)
Permeat are collected for analysis. Identical experiments were
performed with a bare PES support without PP2b, and served as
negative control. The Pb.sup.2+ content in the eluate was
quantified by Inductively-coupled-plasma mass spectrometry
(ICP-MS); in order to minimize contamination, no acid digestion was
performed before ICP-MS analysis.
[0233] Other analytical methods for determining the Pb.sup.2+
content in the eluate are also known to the skilled reader and may
be applied as well: as for example atomic absorption spectrometry
(AAS), atomic emission spectrometry (AES), photometry based on
formation of a colored dithiozon complex; or voltammetry.
Method for Determination of Phosphate (PO.sub.4).sup.3-
Retention:
[0234] For these experiments, membranes of larger dimension (10
cm.sup.2 on NADIR UP150) were prepared. A solution of 200 ppm of
Mg.sub.3(PO.sub.4).sub.2 was prepared in de-ionized water. 150 ml
of this Mg.sub.3(PO.sub.4).sub.2 solution was added into the
permeation cell (45 mm diameter) under continuous stirring. The
permeation cell was pressurized at 2 bar for about 10 minutes and
permeate collected. The conductivity of the initial feed and
permeate were measured with a conductivity meter. The ratio between
the conductivity values was taken as ratio of
Mg.sub.3(PO.sub.4).sub.2 concentration.
[0235] Other analytical methods for determining the
(PO.sub.4).sup.3- content in the feed and permeate are also known
to the skilled reader and may be applied as well: Gravimetric,
Volumetric and Colorimetric methods. A colorimetric method are
based on the formation of an coloured
antimon-phosphormolybdato-complex is defined by EN ISO 6878.
EXAMPLE 1
Preparation of a PP2b Nanofiltration Membrane
[0236] 0.1 mg of PP2b was dissolved in 30 .mu.L of THF. Then 1 mL
of a mixture of water and 3% m/m THF was added at room temperature.
The solution was injected into the 1 mL-volume sample loop of a
multivalve system, and was then flushed by water (water flux of 0.1
mL/min) into a permeation cell carrying in a metal membrane housing
a PES supporting membrane (PES 0.7 cm.sup.2 flat sheet; NADIR type
UP150 membrane, with nominal 150 kDa cut-off). PP2b was deposited
on said support membrane by a water flux of 0.1 mL/min through said
membrane.
[0237] The UV-Vis spectrum (FIG. 1) of the liquid medium before
(black, dotted line) and after the PES membrane (black line)
clearly illustrate that PP2b was quantitatively deposited.
EXAMPLE 2
Control (Reduction) of the PP2b Pore Size by Increasing the Organic
Solvent Content Before/During Deposition
[0238] In order to obtain retention of multivalent ions and
dissolved organic matter, deposition was performed at an increased
organic solvent content of the PP2b solution applied for
deposition. Thereby, the self-assembled (non-covalent,
supramolecular) structures of PP2b as formed before and during
deposition are reduced in size.
[0239] As opposed to the method described in the prior art
(WO2012/025928A1 and Krieg et al, Nature Nanotech 6, 2011, 141),
which is restricted to THF contents around 0.75% (v/v) in water,
according to the present invention significantly increased THF
contents were applied for preparing a PP2b solution in a water/THF
solvent system for performing said deposition.
[0240] The experiment was performed as follows:
[0241] Specifically, as described in Example 1 on a NADIR type
UP150 PES membrane a first PP2b layer was deposited from a
water/THF mixture at 3% (v/v) THF, followed by a second PP2b layer
at 6% (v/v) THF. Each mixture contained PP2b in a concentration of
0.1 mg/mL.
[0242] Such smaller supramolecular structures formed by this method
are only applicable on supporting membranes of suitably small pore
size, like the NADIR type UP150 PES membranes, but not on membranes
with 450 nm pore size, on which they would not deposit but just
pass through.
[0243] In order to demonstrate that this approach really reduces
self-assembled PP2b structures, an Analytical Ultracentrifugation
method was used to quantify the molar mass of the supramolecular
structures at specific THF contents in the water/THF mixture (AUC,
Beckman model XLI, evaluation by Sedfit 14.0, described in Colfen,
H. and A. Volkel (2004). "Analytical ultracentrifugation in colloid
chemistry." Progress in Colloid+Polymer Science 127: 31, and
Schuck, P. (1998). "Sedimentation analysis of noninteracting and
self-associating solutes using numerical solutions to the Lamm
equation." Biophysical Journal 75(3): 1503-1512.).
[0244] As illustrated by the graphical illustration of the analysis
(FIG. 2) said approach effectively reduces the fibrille size
already before deposition. Thus separation membranes with smaller
pore sizes are the result. Quantitatively, we find:
TABLE-US-00001 TABLE 1 THF content *) PP2b fibrils below
10{circumflex over ( )}6 g/mol 1% 8% dash-dotted line 3% 19% dotted
line 6% 56% dashed line 10% 94% solid line *) before and during
deposition
[0245] Thus, by increasing the THF content, it is possible to form
separation membranes with increasingly smaller pore sizes and
consequently reduced permeance.
TABLE-US-00002 TABLE 2 Permeance data of different membrane Per-
meance L/m.sup.2/ No. Typ of composite membrane h/bar 1 PES +
(control, support membrane alone) >300 2 PES + PP2b THF 0.8%
>200 3 PES + PP2b THF 0.8% + PP2b THF 0.8% + PP2b THF 0.8% 57 4
PES + PP2b THF 3.0% + PP2b THF 6.0% (see Example 2) 29 5 PES + PP2b
THF 3.0% + PP2b THF 15.0% 19 6 PES + PP2b THF 3.0% + PP2b THF 15.0%
+ PP2b THF 30% 9 7 PES + PP2b THF 3.0% + PP2b THF 6.0% + 5
EtOH:H.sub.2O 1:1 densification (see Example 3, below)
[0246] Membranes No.2, 3, 5 and 6 were prepared in analogy to
membrane 4, Example 2 by applying PP2b solutions of different THF
content; the PP2b concentration of each solution was 0.1 mg/mL
EXAMPLE 3
Control (Reduction) of the PP2b Pore Size By Densification After
Deposition
[0247] In order to obtain improved retention of multivalent ions
and dissolved organic matter, an already deposited PP2b structure
was partially dissolved in order to reduce the sizes of the
self-assembled (non-covalent, supramolecular) structures of PP2b
after deposition.
[0248] The experiment was performed as follows:
[0249] A single layer or double layer of PP2b (0.1 mg/mL) was
deposited on NADIR type UP150 PES from a water/3% (v/v) THF mixture
as above. Then, a sample loop of 2 mL was filled with 1:1
EtOH:H.sub.2O solution, and was injected at 3 bar pressure and
0.075 mL/min. The obtained membrane was then flushed with at least
2 mL of water.
[0250] On NADIR type UP150 PES we find that the formation of
smaller supramolecular structures (densification) significantly
improves the retention of phosphate and heavy metal ions (see Table
3).
[0251] The formation of denser structures is confirmed by the
observation that the flux decreases: [0252] Flux before
densification: 80 (L/m2/bar/hr) [0253] Flux after densification: 18
(L/m2/bar/hr)
TABLE-US-00003 [0253] TABLE 3 Increased Ion Retention after
Densification Membrane Pb.sup.3+retention (%) PO.sub.4.sup.3-
retention (%) PP2b with densification 12 40 PP2b without
desification 0 21
EXAMPLE 4
PP2b Deposition on INGE Multibore.RTM. Membrane
[0254] A commercial INGE Multibore.RTM. membrane (0.9'') was
applied.
[0255] To deposit PP2b at the inner (active) side of the hollow
bores, the permeate flow is reduced to zero, and the PP2b solution
in water/THF mixture is flushed at 3 mL/min per multibore strand
through the bores (feed flow=retentate flow; permeate flow=0),
until the liquid volume inside the bores is exchanged at least
twice. This ensures homogeneous concentration throughout the length
of the module. Then, the flows are switched to deposition (feed
flow=permeate flow; retentate flow=0). The PP2b solution is thus
deposited by dead-end flow with 3 mL/min per multibore strand onto
the inner side of the bores. In this procedure, the amount of PP2b
is adjusted to 0.12 mg/cm.sup.2 of the module for each layer. In
the laboratory modules with a single multibore membrane strand of
length 15 cm, corresponding to an active surface inside the bores
of 41 cm.sup.2, each layer consisted of 4.5 mg PP2b.
[0256] Two layers are deposited, the first one with 3% THF, the
second one with 6% THF. Then, the densification by flushing with 5
mL of a 1:1 EtOH:H.sub.2O solution is performed at 3 mL/Min. During
this procedure, the pressure is observed to rise to a of 0.3 bar
value (after deposition of the 3% THF layer), to a value of 1.9 bar
(after deposition of the 6% THF layer), and to a value of 4.3bar
(after densification). This final pressure corresponds to a
permeation of 14/m.sup.2/bar/hr. The rising pressure (thus
decreasing permeation) is direct evidence of the gradually reducing
pore sizes.
[0257] The entire deposition is performed at room temperature.
[0258] The successful deposition inside INGE Multibore.RTM.
(surface area 41 cm.sup.2) was confirmed by UV-Vis spectroscopy of
the water that eluted during the deposition process. This was done
with a dead end-flow through the module. Samples were collected at
3 min and 5 min from a single output connecting the two dead-end
outputs. The absence of the Vis-absorption confirms that no PP2b
permeates the membrane i.e. is quantitatively deposited (FIG.
3).
[0259] Homogeneity of deposition was confirmed by photography of a
sacrificed multibore hollow fiber, as taken in the region 10 cm
distant from the injection site (picture not shown). The homogenous
deep red color of deposited PP2b confirms a homogeneous deposition
and the absence of white spots (naked PES) confirm that there was
no negative interference, e.g. of air bubbles.
[0260] Comparing dead-end deposition of PP2b (as in this example)
vs cross-flow deposition of PP2b, optical microscopy images inside
the multibore module show that the PP2b only deposits under
dead-end flow and does not adhere to the supporting membrane if it
is only pumped in cross-flow for 1 h.
[0261] Once deposited, the mechanical stability of the deposited
layer inside the module was investigated. After deposition by the
procedure of this example, the cross-flow speed through the
multibore inner bores was ramped up and down in a range 4 and 10
mL/min. After each change, the permeance in dead-end flow was
determined, and was found to be stable.
EXAMPLE 5
Methylene Blue Retention By Different PP2b Membrane Types
a) Membranes Applied:
[0262] Flat sheet membranes. (0.7 cm.sup.2 and 10 cm.sup.2)
prepared as described in Example 3 INGE Multibore.RTM. (41
cm.sup.2) prepared as described in Example 4
[0263] The flux only minimally increases inside the multibore
module, and is clearly dominated by the PP2B structures, not by the
original PES multibore (which has flux values far above 100, approx
300 L/m.sup.2/bar/h).
b) Measurement of Methylene blue Retention
[0264] Methylene blue (0.002 g/L in water) was filtered dead-end at
pressure below 1bar through PP2b (deposited by the
increased-THF-method, one PP2B layer at 3% THF, a second PP2B layer
at 6% THF) to test the ability of PP2b to filter organics. UV-Vis
spectroscopy showed nearly complete decrease of the methylene blue
peaks at -290 nm and -660 nm. The results are summarized in Table
4.
TABLE-US-00004 TABLE 4 Methylene Blue retention by different PP2b
membranes PP2b mass per Methylene surface area Blue retention Flux
Membrane (mg/cm.sup.2) (%) (L/m.sup.2/bar/hr) Prepared as in Ex. 2
0.24 71.50 24 (3% THF, then 6% THF), (0.12 then densified as in Ex.
3, from each with 0.7 cm.sup.2 layer) Prepared as in Ex. 2 0.24
77.17 33 (3% THF, then 6% THF), then densified as in Ex.3, with
larger area (10 cm.sup.2) Prepared as in Ex.5, 0.24 14.69 - 75.38
51 inside Inge Multibore (41 cm.sup.2)
EXAMPLE 6
PP2b Induced Reduction of Membrane Fouling
[0265] An anti-adsorption effect of PP2B was investigated. The
measurement shows that PP2b very effectively reduces the adsorption
of proteins (from dissolved milk powder) and of humic substance
(from a humic soil extract).
Method:
[0266] Quartz-crystal-microbalance is a standard assay for
adsorption (Lu, Chao, and Alvin Warren Czanderna, eds. Applications
of piezoelectric quartz crystal microbalances. Elsevier, 2012. ISBN
0-444-42277-3 (408 pages)). Quartz crystals were coated stepwise by
Au, then by PES (Ultrason 6020P), then by PP2b (-0.4 g/L in
CHCl.sub.3, spin coated at 1500 rpm, 30 s, 20 .mu.L). At each
deposition step, quartz crystals were withdrawn and subjected to
simulated fouling: [0267] 1. Flushing by water for 10 min. [0268]
2. Flushing/incubation in fouling simulants (Milk powder; humic
acids) for 30 min: pH 7, Flow rate=250 .mu.L/min., 23.degree. C.
[0269] 3. Flushing in water, recording the resonance frequency
change vs. step 1. [0270] 4. Evaluation to adsorbed mass in
ng/cm.sup.2.
[0271] The results are shown in FIG. 4.
[0272] The results indicate a 93% reduction of adsorption,
considered as very successful prevention of fouling.
EXAMPLE 7
PP2b Application to the Filtration of Heavy Metal Ions
[0273] The present results were obtained on PP2b deposited by the
"densification" method on PES flat sheets 0.7 cm.sup.2 area (see
Example 3).
[0274] Solutions of ultrapure water with 50 ppm of different heavy
metal ions were separately prepared from well-soluble salts of
Ni.sup.3+, Cr.sup.3+, Zn.sup.2+, Pb.sup.3+, Ca.sup.2+. A volume of
10 mL of these solutions was injected into the sample loop, pumped
in dead-end filtration through membranes that were freshly prepared
for each of these solutions. The first 3 mL of eluate were
discarded, and the next 5 mL were collected for analysis.
[0275] The heavy metal ion content in the eluate was quantified by
Inductively-coupled-plasma mass spectrometry (ICP-MS) with internal
standards. In order to minimize contamination, no acid digestion
was performed before ICPMS analysis.
[0276] The results are summarized in Table 5.
TABLE-US-00005 TABLE 5 Heavy Metal Ion Retention Ni, Cr, Zn Pb Ca
Flux Retention Retention Retention (L/m.sup.2/ Membrane (%) (%) (%)
bar/hr) Prepared as in Ex. 2 58-70 12 10 24 .+-. 8 (3%THF, then 6%
THF), then densified as in Ex. 3
EXAMPLE 8
PP2b Application to the Filtration of Phosphates
[0277] The following membranes were prepared: [0278] a) with a flat
sheet area of 10 cm.sup.2: [0279] NADIR UP150 PES+PP2b (0.12
mg/cm.sup.2 from 3% THF:H.sub.2O)+PP2b (0.12 mg/cm.sup.2 from 6%
THF:H.sub.2O)+50% EtOH:H.sub.2O (densification treatment) [0280]
NADIR UP150 PES+PP2b (0.12 mg/cm.sup.2 from 3% THF:H.sub.2O)+PP2b
(0.12 mg/cm.sup.2 from 6% THF:H.sub.2O) (as in Example 2) [0281] b)
with INGE Multibore.RTM. (41 cm.sup.2) modules: [0282] Inge
Multibore.RTM. module 2=2.times.PP2b (0.15 mg/cm.sup.2 per layer,
which corresponds to 4.5 mg PP2b at 15 cm length) with 3% and 6%
THF (without EtOH densification treatment). [0283] Inge
Multibore.RTM. module 3=2.times.PP2b (0.15 mg/cm.sup.2 per layer,
which corresponds to 4.5 mg PP2b at 15 cm length) with 3% and 6%
THF, 5 ml 30% EtOH:H.sub.2O (densification treatment). (as in
Example 4)
Method for Water Permeability Testing:
[0284] Distilled water was added into the permeation cell and
pressurized at 1 bar for 30 minutes. Permeate readings were
taken
Method for Rejection Tests:
[0285] 200 ppm of Mg.sub.3(PO.sub.4).sub.2 and MgSO.sub.4 were
prepared.
[0286] 150 ml of Mg.sub.3(PO.sub.4).sub.2 was added into the
permeation cell under continuous stirring. The permeation cell was
pressurized for about 10 minutes and the permeate was collected.
The conductivity of the initial feed and the permeate were measured
with a conductivity meter. The permeation cell was rinsed with DI
water and DI water was pressurized at 1 bar for cleaning of the
membrane.
[0287] The steps were repeated for MgSO.sub.4.
TABLE-US-00006 TABLE 6 10 cm.sup.2 Membrane results:
Mg.sub.3(PO.sub.4).sub.2 MgSO.sub.4 Water flux retention retention
Membrane (L/m.sup.2/hr/bar) (%) (%) PP2b + EtOH 56.1 40.0 6.0 PP2b
380.5 .+-. 62.5 20.8 .+-. 0.2 2.6 .+-. 0.1
[0288] The results demonstrate that the densification procedure
increases the membrane performance for phosphate retention.
TABLE-US-00007 TABLE 7 INGE Multibore module results Mg.sub.3 Water
(PO.sub.4).sub.2 Mg.sub.3 MgSO.sub.4 INGE Per- Per-
(PO.sub.4).sub.2 Per- MgSO.sub.4 Multi- meability meability Reject-
meability Reject- bore (L/m.sup.2/ (L/m.sup.2/ ion (L/m.sup.2/ ion
ID hr/bar) hr/bar) (%) hr/bar) (%) module 2 65 60 29.9 60 3.4
module 3 44 32 35.9 33 4.0
[0289] The results obtained for INGE multibore are consistent with
the flat sheet results and confirm that the deposition was
effective despite the more complex procedure and morphology inside
the multibore system, and again confirm that the densification
increases the membrane performance.
EXAMPLE 9 (Comparative)
Investigating Applicability of PP2b Layers Obtained According to
WO2012/025928 for the Filtration of Heavy Metals and Organic
Dyes
a) Heavy Metal Filtration
[0290] Using PP2b in H.sub.2O (containing 0.9% THF), a layer was
deposited on a support (PES) with a pore size of 0.45 .mu.m as
suggested in WO2012/025928. The absence of red color of the eluate,
the observed pressure increase of up to 0.57 bar (at 0.2 mL/min),
and finally the red Perylene layer on the support all indicate a
successful deposition of PP2b (consistent with WO2012/025928).
[0291] On thus prepared membranes, one individually for each metal,
10 mL of aqueous solutions of three different heavy metals (Cr, Ni,
Zn) at 50 ppm metal content were filtered. The content of heavy
metal was determined by ICPMS in the eluate and in the original
solution.
[0292] A difference of that less than 1 ppm (corresponding to less
than 2% retention, i.e. practically zero retention of heavy metals)
was observed.
[0293] This confirms that the process and material described in the
prior art are not effective to filter heavy metals and thus differ
from the teaching of the present invention significantly.
b) Methylene Blue Filtration:
[0294] Using PP2b in H.sub.2O (containing 0.9% THF), a layer was
deposited on a support (PES) with a pore size of 0.45 .mu.m as
suggested in WO2012/025928. The absence of red color of the eluate,
and the red Perylene layer on the support all indicate a successful
deposition of PP2b (consistent with WO2012/025928).
[0295] Then, 5 mL of a solution of methylene blue at 5 mg/L are
filtered. The first 2 mL are discarded. The next 2 mL elution is
measured by UV VIS spectrometry, finding no reduction of dye
absorption by the PP2b layer.
[0296] This confirms that the process and material described in the
prior art are not effective to filter the dye and thus differ from
the teaching of the present invention significantly.
[0297] The disclosure of herein cited documents is incorporated by
reference.
* * * * *